ELECTRICAL PARAMETERS LIST WITH CAUSE EFFECT - SOLUTIONSS.NOParameterDefinitionRangeCauseEffectSolution

Metering Data:

1Voltage (V)Voltage is the electrical driving force set up by an electric potential difference. Normal operations: Service Voltage: 5%Utilization Voltage: +5% to -8.33% Short duration: Service Voltage: +5.83% to -8.33%Utilization Voltage: +5.83% to -11.67%

Remarks:for 3-phase 415 V p-pFor 1-phase 230 V p-n

Voltage unbalance at the motor terminals should not exceed 1% Open Delta transformers Unbalanced loading (Mixed single and three phase loading) Unequal tap settings on transformers High resistance connections Blown fuses on capacitor banksRemarks: 1% voltage unbalance will increase the motor losses by 5%.

Note: 1. Small motors, single phase motors are more sensitive to over-voltage and saturation than large motors.2. Two pole and four pole motors tend to be less sensitive to high voltage than six pole and eight pole designs.

Over-voltage can drive up amperage and temperature even on lightly loaded motors. Thus, motor life can be shortened by high voltage. Full load efficiency drops with either high or low voltage. Power factor improves with lower voltage and drops sharply with high voltage. Inrush current goes up with higher voltage. Damage to protective devices. Electrical Fire Hazards 10% voltage decrease would cause a 10% amperage increase in motors. A 5% increase in voltage results in a 50% reduction in bulb life

Provide voltage regulation to keep the steady state voltage within the ranges. Adjust the transformer tap settings Online monitoring system. Distribution of loads on all phases equally. Frequent checking of capacitors banks health. Maintain Records.

2Line Voltage (VLL)

Line voltage is stated as "phase to phase"VLL = 1.732 times of phase voltage

Remarks: for 3-phase 415 V

3Average voltage (Vavg)Its an average value of all the 3 line or phase voltages.Remarks: Useful for analyzing Voltage unbalance & direct glance of average incoming voltage

4Phase voltage (Vp)Phase voltage is stated as "phase to groundRemarks: Nominal phase voltage is 230V (across any phase to ground)

5Current (I)Anelectric currentis a flow ofelectric chargearound a circuit. Unit is amperes (A).

I = kVA/(VxPF)I = kW/ V

Where kVA=Apparent powerkW=Active powerV=voltagePf=power factorCauses for higher Current flow are Over voltage Low power factor Increased harmonics Rewinded motors Equipment derating Short circuit Current leakage in circuits Derating of equipments efficiency Equipment Life reduces Over heating of conductors. Electrical Fire Hazards Overheating of neutral cables. Higher power consumption than rated. Motor-heating & winding damages Lamps may damge Sensitive equipments malfunctioning Power factor correction Replacing with energy efficient devices. Optimizing operating voltage levels Check for harmonics Maintain records

6Average Current (I avg)Its an average value of all the 3 line currentsRemarks: Useful for analyzing Current unbalance in phases & direct glance of average incoming Current in phasesAvg Current = (I phase1 + I phase2 + I phase3)/3

7Current in Neutral Line (In)Indicates the value of current flown in a neutral wire in case of a 3-phase with neutral wire connection.If the loads on all phases are equal, there will not be any current flow in neutral.

Unbalanced load in phases Third order Harmonics

If the unbalance is severe, then individual loads may be subject to over-voltages or under-voltages. power feeders & transformers can be overloaded Voltage distortion Common mode noise Neutral lines heating

Balance the load equally in all 3 phases. Use Harmonic filter Increasing neutral conductor size

8FrequencyUnit of frequency in Cycles per secondDeviation should be less than +/- 5% of the nominal value.

From EB supply DG set frequency set-point Inverter trigger/output frequency settings

Operating induction motors at frequencies above nominal rating results in Increased speed, increased operating temperatures, decreased functional horse power and Potentially shortened motor life.

At frequencies above nominal rating results in Over-excitation of generators with severe heating as a result. reduced motor speed Flickering of lights

Note: Temperature can rise as much as ten degrees Celsius per every 10 percent increase in the motor frequency Adjust the frequency in case of DG set operation. EB shall fulfill its partial responsibility in EB supply frequency Adjust inverter settings in case of UPS systems

9Power factor The ratio of real power (kW) to apparent power (kVA) for any given load and time.

Inductive loads - consumes reactive power.

Capacitive loads generates reactive powerIdeally, the power factor should be unity(or, >0.99 PF lagging) Partial/ No loaded motors will have generally lower pf. Arc & electric discharge lamps , industrial heating furnaces, AC motors, transformers, fans, welding equipment, extruders and injection machines, presses and stamping equipment as well as ballasted lighting. Using old & inefficient motors re-winded motors after burn out. Load imbalance on the phases. Harmonics also cause to lower PF. Operation on low load period Capacitor bank failures/improper rating Operating equipment with over voltage Increased current drawn for producing same output power. Larger capacity supply line, transformer, and power usage therefore added costs. Increase of the cost of use for electricity. Overheating in the neutral cables of three-phase systems. Increased losses in power cables. Penalty for lower PF Increased kVA demand Increased fire hazards Frequent tripping of circuit breakers & fuse blown Motor-heating & winding damages.

Online monitoring system Installing APFC (Automatic power factor controllers), or reactive power (kVAR) generators into the electrical distribution system Minimizing operation of idling or lightly loaded motors. Avoiding operation of equipment above its rated voltage. Replacing standard/ Rewinded motors with energy-efficient motors. Install harmonic filters

10Energy consumption (kWh)1kWh is the power(kW) consumed of an equipment for a duration of 1 hourRemark: Energy consumption(kWh) = power x Time Where power in kW & Time in hours

11Voltage Unbalance / Unbalance factorIn a 3-phase distribution, if the current or voltages RMS are not the same or the deference between a 3 phase angle is not 120 degrees, we call the phase voltages or current unbalance.

Generally, the difference between the highest and the lowest voltages should not exceed 5% of the average voltage.

Percent Unbalance = 100 x Max Deviation from Average Voltage/ Average Voltage

Note: 1% voltage unbalance will increase the motor losses by 5%. Voltage unbalance at the motor terminals should not exceed 1%

Open Delta transformers Unbalanced loading (Mixed single and three phase loading) Unequal tap settings on transformers High resistance connections Blown fuses on capacitor banks Overheating of components ; especially motors Derating of the induction motor. Once unbalance reaches 5%, the temperature begins to rise so fast Shorten equipment life. Intermittent shutdown of motor controllers. Additionally, excessive current imbalance due to supply voltage imbalance can cause nuisance tripping of motor protective devices A 10% drop in terminal voltage from the rated, will reduce the Induction motor torque by approx 19%, increase full load current by approx 11%, and reduce overload capacity. Current unbalance leads to current flow in neutral wire, thus induces harmonics & creates neutral wire heating Electrical fire hazards Damages to protective devices Transformer overloading 10% voltage decrease would cause a 10% amperage increase in motors. A 5% increase in voltage results in a 50% reduction in bulb life

The first place to look is not the power company. Instead, look for electrical distribution systems. Continuous monitoring Check single phase loads are evenly balanced across the phases. Look for in-line reactors installed to correct imbalances. These reactors usually have taps for adjustment Apply voltage-regulating equipment, such as LTC transformers and bus or circuit voltage- regulating equipment, at the substation Eliminating motor rewinding Frequent monitoring of capacitor banks health

12Current Unbalance / Unbalance factorIn a 3-phase distribution, if the current or voltages RMS are not the same or the deference between a 3 phase angle is not 120 degrees, we call the phase voltages or current unbalance Generally, the difference between the highest and the lowest Current in phases should not exceed 10% of the average value.

Percent Unbalance = 100 x Max Deviation from Average Current/ Average Current

Voltage Unbalance Loose terminal connection or a build-up of dirt or carbon on one set of the contacts. Unbalanced Rewinding of motors Overheating of components ; especially motors Derating of the induction motor. Once unbalance reaches 5%, the temperature begins to rise so fast Shorten equipment life. Intermittent shutdown of motor controllers. Additionally, excessive current imbalance due to supply voltage imbalance can cause nuisance tripping of motor protective devices A 10% drop in terminal voltage from the rated, will reduce the Induction motor torque by approx 19%, increase full load current by approx 11%, and reduce overload capacity. Current unbalance leads to current flow in neutral wire, thus induces harmonics & creates neutral wire heating Electrical fire hazards Transformer overloading

Continuous monitoring Check single phase loads are evenly balanced across the phases. Look for in-line reactors installed to correct imbalances. These reactors usually have taps for adjustment Apply voltage-regulating equipment, such as LTC transformers and bus or circuit voltage- regulating equipment, at the substationEliminating motor rewinding

13Power or Active power (P)Active (Real or True) Poweris measured in watts (W) or kW and is the power drawn by the electrical resistance of a system doing useful work

Power consumption should be Total connected load.

Ideally, Active power= Apparent power (at unity PF)Causes for higher power consumption are Usage of inefficient equipments/utilities Older technology Low power factor Over design of equipments. Operating at partial load. Overloaded operation Over voltage Improper operation & maintenance. No Energy Management Equipment derating Supply & consumption load mismatch. power loss in cables Harmonics

Higher energy consumption results in Possibility of maximum demand exceeding the contract demand. Increased monthly bills Increased process cost per unit of production Transformer overloading Derating of equipments lifetime.

Online Energy monitoring system. Operating the equipments at maximum efficiency. Reduction of Auxiliary Power Consumption Use VFD/multi speed in case of variable motor loads. utilizing natural resources for lighting & ventilation Avoid running utilities at no-load. switching off unnecessary lights, fans/ACs, etc., Proper Energy management Improved power factor Replacing old energy inefficient utilities with low energy consumption products. Install maximum demand controller(MDC) Replace existing electric heaters with fuel based/solar based heating. Avoid leakages in case of compressed air system. Replace existing inefficient systems with energy efficient ones. Adopting energy saving mechanism/procedures for existing utilities for performance improvement. Reduce Harmonics in circuit. Operate Equipments at equipments rated voltage Eliminate loose contacts at terminals. Using dimmers for lighting systems. Use day light harvesting /Occupancy sensors. Optimize the room temperature in ACs. Use high conductive materials like copper for circuit wirings. Install master switches. Optimize the distance between load and power mains to minimize cable losses. Install Renewable energy systems (like solar, wind, biomass, etc) Optimize the water pump running hours by efficient water usage techniques. Eliminate leaks in liquid/air flow system. Employ Torque controller/ energy savings mechanism on motors. Use flat belts/ Cogged V-belts for transmitting maximum power in motors. Installing energy efficient motors

14Inductive Reactive power (Q) kVAR (or) rkVA (or) kilovar.

Reactivekilovolt-amperes do no work but must be supplied to magnetic equipment, such as motors, relay & transformers to produce the magnetizing flux.

As low as zero Or,For Unity PF, Q=0 Low power factor Absence of Capacitor banks. Under-sized power factor controllers. High inductive loads Non-linear loads such as Electronic ballasts, UPS, motors, VFDs etc., In presence of Harmonics. Rewinded motors

Penalty for low PF results in voltage drop Increased cable losses Electrical fire hazards Penalties for kVA demand exceeding the sanctioned value. Transformer & Cables overloading. Frequent tripping of Circuit breakers & Fuses. Electrical fire hazards Damage to protective devices.

Online monitoring of power factor Installing APFC (Automatic power factor controllers) Minimizing operation of idling or lightly loaded motors. Avoiding operation of equipment above its rated voltage. Replacing standard/ Rewinded motors with energy-efficient motors Minimize inductive loads Eliminate harmonics Install Reactive power generators near the load terminal for highly inductive utilities. Install Non-linear loads having higher power factor Installing energy efficient motors

15Capacitive Reactance For a Capacitive load we say it has leading reactive power. Useful for Power factor correction.Capacitive reactance should be less than or equal to Inductive reactanceFor generating reactive power Compensates the Reactive power required by the inductive load. Improves power factor. Oversized manual operated power factor corrector will results in leading PF Possibility of over voltages in case of capacitive loads. Over voltage may cause damage to utilities Capacitive loads will demagnetize or derate the motors Reduces the peak kVA demand Avoids the penalties of Power factor & peak kVA demand exceeding sanctioned demand. Electrical fire hazards

Online monitoring of power factor Switch to APFC device for better PF maintenance. Down size/oversize capacitor bank in case of manual operated to optimum level to maintain the PF near unity. Minimizing operation of idling or lightly loaded motors. Operate utilities at maximum efficiency. Eliminate harmonics Install Non-linear loads having higher power factor Installing energy efficient motors

16Apparent power (kVA)Apparent Poweris measured in volt-amperes (VA) and is the voltage on an AC system multiplied by all the current that flows in it. kVA should be equal to kW consumption at unity power factor. Pf> 0.98 is advisableHigher kVA consumption is due to increased Reactive power consumption/ low PF energy inefficient equipments No Energy Management low / partial loaded motors Absence of power factor controller highly inductive/ low PF generating loads(non-linear loads) Increased line losses presence of harmonics High kW, KVA consumption. Possibility of maximum demand exceeding the contract demand leading to penalty. Penalty for lower power factor Increased cable losses Electrical fire hazards Transformers & Cables overloading Utility lifetime comes down. Damage to protective devices.

Online monitoring of Energy consumption Peak load shaving/ reschedule to avoid maximum demand penalty. Install maximum demand controller Replace old energy inefficient equipments with newer ones power factor control Eliminate harmonics Operate equipments at full load & maximum efficiency Eliminate cable losses

17Consumption energy

Remarks: Its the energy imported / power consumption from power grid or generating station by the utilities.

18Generation energy

Remarks: Its the electrical energy exported/delivered by generating,from otherforms of energy to the grid or power consuming utilities

19Four quadrant operationDisplays energy importing or exporting details in a four quadrant graphical manner

Remarks: A four quadrant metering system is the metering of bi-directional energy flow. Active import while reactive import (PF lag) Active Export while reactive import (PF Lag) Active export while reactive export (PF lead) Active import while reactive export(PF lead)

Also it provides information about Consumption energy Generation energy Total energy Net energy The absorption reactive energy The generation reactive energy Total reactive energy Net reactive energy Total apparent energy

20% of Load It displays the % of operating load w.r.t actual connected load at the panel where metering is clamped. Loading is based on Current(A) basis.Opearting load should be less than or equal to Connected load.Increased load may be due to Additional auxiliary load/running standby unit also. Machine/ motor over loaded Reduced efficiency of utilities Addition of new utilities to the existing ones. Low power factor Presence of harmonics Short circuit or leakages

Higher kW & kVA consumption. Waste of Energy Exceeding maximum demand & penalities for those damage to overloaded equipments Electrical fire hazards Transformer & Cables overheating. Damage to protective devices. Frequent tripping of MCB & fuses. Higher cable losses Online energy monitoring system Switch off idle running/unnecessary loads Install Maximum demand controllers. Replacing existing energy inefficient utilities with energy efficient ones. Minimize line losses. Improve power factor Reduce harmonics Scheduled operation of loads. Running equipments at its maximum efficiency Minimize partial running/ no loaded motor running

21Voltage/Current phase angle For a 3 phase supply, the phase angle difference between the adjacent phases will be 120o

Useful for to analyze the phase deviation w.r.t Current phase angle for PF analysis Voltages/ Current have equal amplitudes but are separated by a phase angle of 120o.

For Unity power factor, Voltage & current must be in phase.

Inductive/ Capacitive reactance Higher kVAr consumption Possibility of consumption kVA exceeding the sanctioned demand Penalties for higher kVA consumption Penalty for low power factor Increased cable loss Electrical fire hazards Transformer & Cables overloading. Improve power factor Optimize inductive loads Eliminate harmonics Running equipments at its maximum efficiency Minimize partial running/ no loaded motor running

22Phase sequenceIn 3-phases supply, each phase will be provided with some notation & a order of sequence (R,Y & B)Phase sequence should be in R, Y & B for 3-phase utilitiesPhase sequence disorder may be due to rewiring of existing system Negativephase sequence components causes Reversal of rotation direction. Decrease in the torque developed by the motor. Draws higher current for the same mechanical load Causes surface heating which can lead to motor damage. Installation of negativephase sequence relays Color coding for all 3 phases

Harmonic Data:

23Waveform distortion / THD (Total Harmonic Distortion) Defined as the ratio of the sum of the powers of all harmonic components to the power of the fundamental frequency.

Power line harmonics are generated when a load draws a non-linear current from a sinusoidal voltage The ideal sine wave has zero harmonic components.

Total harmonic current limits to 8% and total harmonic voltage limits to 5%.

The objectives of the current limits are to limit the maximum individual frequency voltage harmonics to 3% of the fundamental and the voltage THD to 5% for systems and 3% for any single harmonic

Switched mode power suppliesImproper design of existing Harmonic suppressing devices Dimmers Current Regulators Frequency Converters Voltage source inverters with pulse width modulated converters Low power consumption lamps Electrical arc-furnaces Arc welding machines Induction motors with irregular magnetizing current associated with saturation of the iron All equipment with built-in switching devices or with internal loads with non-linear voltage/current characteristic loads such as electronic ballasts, computer power supplies, fax machines, power Inverters, and variable frequency drives (VFDs).

Higher temp. in neutral conductors and distribution transformers. Additional core loss in motors which results in excessive heating. Interfere with communication transmission lines Shorten the life of electronic equipment and cause damage to power systems. Overheating of electrical distribution equipment, cables, transformers, standby generators, etc. High voltages and circulating currents caused by harmonic resonance Equipment malfunctions due to excessive voltage distortion False tripping of branch circuit breakers Metering errors Fires in wiring and distribution systems Generator failures Crest factors and related problems Lower system power factor, resulting in penalties on monthly utility bills capacitor failure Signal sensitive equipments can results in malfunction. Online power quality monitoring system Install the Active / Passive / Integrated Harmonic Filters. Redesign the existing faulty harmonic suppressor. Check filters health often. Go for k-rated Transformers

24Odd/ Even Harmonic distortionof voltage

The signals at frequencies of 3f, 5f, 7f, etc. are called odd harmonics and Signals occurring at frequencies of 2f, 4f, 6f, etc. are called even harmonics.

The limits for individual harmonics are given in the attached files.

For Voltages THD of individual signals shouldnt exceed 3% of fundamental frequency.

If a third harmonic is present in the system, it is likely the result of single phase loads or phase imbalances. Non-linear loads like VFDs, Ballasts, UPS, Office equipments, etc., Low power factor Neutral conductor overloading. Additional core loss in motors which results in excessive heating. Interfere with communication transmission lines Shorten the life of electronic equipment and cause damage to power systems. Overheating of electrical distribution equipment, cables, transformers, standby generators, etc. High voltages and circulating currents caused by harmonic resonance Equipment malfunctions due to excessive voltage distortion False tripping of branch circuit breakers Metering errors Fires in wiring and distribution systems Generator failures Crest factors and related problems Lower system power factor, resulting in penalties on monthly utility bills capacitor failure Signal sensitive equipments can results in malfunction.

Continuous power quality monitoring Install the Active /Passive/ Integrated Harmonic Filters based on the harmonic levels. Redesign the existing faulty harmonic suppressor Check filters health often. Go for k-rated Transformers

25THFF (Telephone Harmonic Form Factor)The harmonic interference may cause noise in the system and affects the quality of communication It is 0 with no harmonic. Our hearing and the telephone cannot respond well to the 50Hz current and voltage but can respond better to about 1 kHz current and voltage.

Induced harmonics in the distribution systems. Non-linear loads like VFDs, Ballasts, UPS, Office equipments, etc., Will cause noise in the system and affects the quality of communication Signal sensitive equipments can results in malfunction. Harmonic filters should be installed to eliminate higher ordered frequency currents in power mains. Check filters health often.

26CF (Crest Factor)

The Crest Factor is equal to the peak amplitude of a waveform divided by the RMS value. The purpose of the crest factor calculation is to give an analyst a quick idea of how much impacting is occurring in a waveform.

In a perfect sine wave, the crest factor is equal to 1.41. Crest factors with a value higher than 1.41 imply that there is some degree of impacting. It is generally between 1.5 and 2 and can even reach 5 in critical cases.

The crest factor for a non-sinusoidalcurrent waveform can differ dramatically for loads that are not power factor corrected, such as a switching power supply or lamp ballast, which give a current waveform that is short in duration but high in amplitude Impacting is often associated with roller bearing wear, cavitations and gear tooth wear. High crest factor causes overheating of power supply components also. A high crest factor signals high transient over currents which, when detected by protection devices, can cause nuisance tripping. Damage to protective devices.

Harmonic filters should be installed Check filters health often. Eliminate or reduce the bearing wear, wear, cavitations and gear tooth wear. Quite often, the Crest Factor is trended over time in order to see if the amount of impacting is increasing or not.

27K-factor of the current K-factor is a weighting of the harmonic load currents according to their effects on Transformer heating. Therefore, it is the percentage amount of odd harmonics (3rd, 5th, 7th ,.., 25th,..) present in the load which can affect the transformer, and this condition is called a Non-Linear Load or Non-Sinusoidal Load.

A K-factor of 1.0 indicates a linear load (no harmonics). The higher the K-factor, the greater the harmonic heating effects.

The total amount of harmonics will determine the percentage of non-linear load, which can be specified with the appropriate K-Factor rating. Induced harmonics in the distribution systems. Non-linear loads like VFDs, Ballasts, UPS, Office equipments, etc., Overheating problems on cables & equipments that connected to harmonic generated feeders. Harmonics that generated by Non-linear loads will substantially increase transformer losses. High distribution losses. Low power factor Electrical fire hazards Online monitoring system. Install Harmonic suppressing devices. Install high K-rated Transformers.

28Flickering Flicker is a very specific problem related to human perception and incandescent light bulbs. 3 Types of flickering Continuous flickering: Lights that flicker several times a second Cyclic flickering: Lights that flicker one to two times per minute Intermittent flickering: Lights that flicker infrequently, typically once or more per hour Pst is a value measured over 10 minutes. Compatibility level for short term flicker (Pst) is 1.0. Plt is derived from 2 hours of Pst values. Compatibility level for long term flicker (Plt) is 0.8 Florescent lights, Welders, Arc Furnaces. Laser Printers, Copiers, Bad Breakers, Bad Connections. Motor(s) Starting Switching a capacitor bank failing ballasts arcingsomewhere

light flickering Electrical fire hazards Visibility related problems at Workplaces.

Voltage regulation Avoid loose connections & arcing Replace defective ballasts

Power Optimisa (Pty) Limited Registered number: 2008/001541/07 VAT number: 4890244983

Contact details:

Phone: +27 (0) 21 403 6360 Mobile: +27 (0) 78 1652452 EMail: info@poweroptimisa.com Fax: +27 (0) 21 403 6361

Power Optimisa 2009

ELECTRIC MOTORS AND VOLTAGE

Effects of low and high voltage on motors and the related performance changes

There are many undesirable things that happen to electric motors and other electrical equipment as a

result of operating a power system in an over voltage manner. Operating a motor beyond its nominal range

of its voltage requirements will reduce its efficiency and cause premature failure. The economic loss from

premature motor failure can be devastating. In most cases, the price of the motor itself is trivial compared

to the cost of unscheduled shutdowns of the process. Both high and low voltages can cause premature

motor failure, as well as voltage imbalance.

So the best life and most efficient operation occur when motors are operated at voltages close to the

nameplate ratings. This is where POWER OPTIMISA can beneficially impact a whole site, not only by

reducing the cost of the electricity bill, but also by extending the life of the electrical motors while

preventing unexpected failures.

EFFECTS OF HIGH VOLTAGE*

One of the basic things that people assume is, that since low voltage increases the amperage draw on

motors, then by the same reasoning, high voltage would tend to reduce the amperage draw of the motor.

This is not the case [see graph below]. High voltages on a motor tends to push the magnetic portion of the

motor into saturation. This causes the motor to draw excessive current in an effort to magnetize the iron

core beyond the point to which it can easily be magnetized. This generally means that the motors will

tolerate a certain change in voltage above the design voltage, but extremes above the designed voltage

will cause the amperage to go up with a corresponding increase in heating and a shortening of motor life.

For example, many motors are rated at 220/230 volts and had a tolerance band of plus/minus 10%. Thus,

the actual voltage range that they can tolerate on the high voltage connections would be at least 207 volts

to 253 volts. Even though this is the so-called tolerance band, the best performance of larger motors would

occur at or near the rated voltage. The extreme ends, either high or low, would be putting unnecessary

stress on the motor.

Generally speaking, these voltage tolerance ranges are in existence, not to set a standard that can be used

all the time, but rather to set a range that can be used to accommodate the normal hour-to-hour swings in

received voltage. An operation of a motor on a continuous basis at either the high extreme or the low

extreme will shorten the life of the motor.

Although this paper covers the effects of high and low voltage on motors, the operation of other magnetic

devices is often affected in similar ways. Solenoids and coils used in relays and starters are punished by

high voltage more than they are by low voltage. This is also true of ballasts in fluorescent, mercury, and

high pressure sodium light fixtures. Transformers of all types, including welding transformers, are damaged

in the same way. Incandescent lights are especially susceptible to high voltage conditions. A 5% increase in

voltage results in a 50% reduction in bulb life. A 10% increase in voltage above the rating reduces

incandescent bulb life by 70%.

Overall, it is definitely in the equipments best interest to have incoming voltage close to the equipment

ratings. High voltage will always tend to reduce power factor and increase the losses in the system which

results in higher operating costs for the equipment and the system.

Power Optimisa (Pty) Limited Registered number: 2008/001541/07 VAT number: 4890244983

Contact details:

Phone: +27 (0) 21 403 6360 Mobile: +27 (0) 78 1652452 EMail: info@poweroptimisa.com Fax: +27 (0) 21 403 6361

Power Optimisa 2009

The graph shown in Figure 1 is widely used to illustrate the general effects of high and low voltage on the

performance of T frame motors. It is okay to use the graph to show general effects but, bear in mind

that it represents only a single motor and there is a great deal of variation from one motor design to the

next. For example, the lowest point on the full load amp line does not always occur at 2-1/2% above rated

voltage. On many motors it might occur at a point 2% to 3% below the rated voltage. Also the rise in full

load amps at voltages above the rated, tends to be much steeper for some motor winding designs than

others.

LOW VOLTAGE*

When electric motors are subjected to voltages below the nameplate rating, some of the characteristics

will change slightly and others will change more dramatically. A basic point to note is that to drive a fixed

mechanical load connected to the shaft, a motor must draw a fixed amount of power from the power line.

The amount of power the motor draws is roughly related to the voltage x current (amps). Thus, when

voltage gets low, the current must get higher to provide the same amount of power. The fact that current

gets higher is not alarming unless it exceeds the nameplate current rating of the motor. When amps go

above the nameplate rating, it is safe to assume that the buildup of heat within the motor will become

damaging if it is left unchecked. If a motor is lightly loaded and the voltage drops, the current will increase

in roughly the same proportion that the voltage decreases. If voltages go too low Power Optimisa have a

model that will tap them up.

For example, say a 10% voltage decrease would cause a 10% amperage increase. This would not be

damaging if the motor current stays below the nameplate value. However, if a motor is heavily loaded and

a voltage reduction occurs, the current would go up from an already fairly high value to a new value which

might be in excess of the full load rated amps. This could be damaging. It can thus be safely said that low

voltage in itself is not a problem unless the motor amperage is pushed beyond the nameplate rating. Ie/ it

must be controlled in a safe range.

Power Optimisa (Pty) Limited Registered number: 2008/001541/07 VAT number: 4890244983

Contact details:

Phone: +27 (0) 21 403 6360 Mobile: +27 (0) 78 1652452 EMail: info@poweroptimisa.com Fax: +27 (0) 21 403 6361

Power Optimisa 2009

Aside from the possibility of over-temperature and shortened lifespan created by low voltage, some other

important items need to be understood. The first is that the starting torque, pull-up torque, and pull-out

torque of induction motors, all change based on the applied voltage squared . Thus, a 10% reduction from

nameplate voltage (100% to 90%, 230 volts to 207 volts) would reduce the starting torque, pull-up torque,

and pull-out torque by a factor of .9 x .9. The resulting values would be 81% of the full voltage values. At

80% voltage, the result would be .8 x .8, or a value of 64% of the full voltage value. In this case, it is easy to

see why it would be difficult to start hard-to-start loads if the voltage happens to be low. Similarly the

motors pull-out torque would be much lower than it would be under normal voltage conditions.

To summarise: low voltage can cause high currents and overheating which will subsequently shorten

motor life. Too low voltage can also reduce the motors ability to get started and its values of pull-up and

pull-out torque. On lightly loaded motors with easy-to-start loads, reducing the voltage will not have any

appreciable effect except that it might help reduce the light load losses and improve the efficiency under

this condition. The Power Optimisa helps protect in this circumstance.

Some general guidelines might be useful:

1. Small motors tend to be more sensitive to over-voltage and saturation than large motors.

2. Single phase motors tend to be more sensitive to over-voltage than three phase motors.

3. Older U-frame motors are less sensitive to over-voltage than newer T frames.

4. Premium efficiency Super-E motors are less sensitive to over-voltage than standard efficiency motors.

5. Two pole and four pole motors tend to be less sensitive to high voltage than six pole and eight pole

designs.

6. Over-voltage will drive up amperage and temperature even on lightly loaded motors. Thus, motor life

will be shortened by high voltage.

7. Full load efficiency drops with either high or low voltage.

8. Power factor improves with lowering voltage and drops sharply with lowering from high voltage levels.

9. Inrush current goes up with higher voltage.

*This text is an adaptation of The Cowern Papers, ownership of Baldor Electric Co**., Wallingford, Conn.,

(http://www.baldor.com/pdf/manuals/PR2525.pdf)

** Baldor Electric Company is global renowned designer, manufacturer and marketer of industrial electric

motors, power transmission products, drives and generators. It is listed in the New York Stock exchange

POWER OPTIMISAs effect on an AC motor

Induction motors (single phase or 3 phases) account for most of the industrial, commercial and residential

appliances like refrigerators, air conditioning, air compressors, and pumps among others. These motors

have five major components of loss; Iron loss, Copper loss, Frictional loss, windage loss and sound loss. All

these losses add up to the total loss of the induction motor. Frictional loss, windage loss and sound loss are

constant, independent of shaft load, and are typically very small. The major losses are Iron loss and Copper

Loss. The iron loss is essentially constant, independent of shaft load, while the copper loss is an I2R loss

which is shaft load dependent. The iron loss is voltage dependent and so will reduce with reducing voltage.

For a motor with a 90% full load efficiency, the copper loss and iron loss are of the same order of

magnitude, with the iron loss typically amounting to 25 - 40% of the total losses in the motor at full load. If

we consider for example, an AC motor with a full load efficiency of 90%, then we could expect that the iron

loss is between 2.5% and 4% of the motor rating.

By optimizing the voltage on a motor, which was operating at less than maximum efficiency, the POWER

OPTIMISA effects result in a reduction of the iron loss of the motor. In a case where the motor has a very

high magnetizing current, there can be a reduction in copper loss also. By managing the voltage and

voltage balance, the motor efficiency will be improved.

POWER OPTIMISA will thus reduce the stress and losses on motors so they operate at their maximum

efficiency (close to their nameplate rating), and assuring steady power output. This will reduce

Power Optimisa (Pty) Limited Registered number: 2008/001541/07 VAT number: 4890244983

Contact details:

Phone: +27 (0) 21 403 6360 Mobile: +27 (0) 78 1652452 EMail: info@poweroptimisa.com Fax: +27 (0) 21 403 6361

Power Optimisa 2009

maintenance costs for the lifetime of the motor. Through the more efficient operation of the motors, there

will also be a reduction in the amount of reactive power (kVAr) consumed which will improve the power

factor. POWER OPTIMISA manages to save the energy that is being wasted while proving the best power to

power to the motor.

POWER OPTIMISAs effect on motors with inverter drives or variable speed drives

As with AC motors, the POWER OPTIMISA will reduce the stress on VSDs (inverter drives) by delivering an

optimized voltage. There will be no effect on speed or torque of the motor as it is buffered by the inverter.

The life span of these types of drive will be shortened considerably if the supply voltage is too high or

fluctuating, and many sites report the need to replace such expensive drives frequently. By correcting this

problem, the POWER OPTIMISA will significantly reduce equipment replacement costs. VSDs and inverter

drives are also notorious for generating harmonics, which can damage sensitive equipment. As the

POWER OPTIMISA is able to attenuate THDs via filter harmonics, the damaging effect of these drives can

be limited.

Four-Quadrant Power flow

Harmonic Voltage distortion standards for various buildings

Harmonic Limits for currentClassification of equipmentEquipment can be grouped into one of 4 classes based on the following criteria as evaluated by theIEC committee members: Number of pieces of equipment in use (how many (volume) are being used by consumers) Duration of use (number of hours in operation) Simultaneity of use (are the same type of equipment used on the same time frame) Power consumption Harmonics spectrum, including phase (how clean or distorted is the current drawn by the equipment)

After all the above criteria are taken into consideration equipment are classified as follows:

Class A Balanced three-phase equipment Household appliances, excluding equipment identified by Class D Tools excluding portable tools Dimmers for incandescent lamps Audio equipment Everything else that is not classified as B, C or DClass B Portable tools Arc welding equipment which is not professional equipmentClass C Lighting equipmentClass D Personal computers and personal computer monitors Television receiversNote: Equipment must have power level 75W up to and not exceeding 600W

Table: Harmonic Limits

Limits of Harmonic Current Distortion (%)Harmonic Order(n)P > 10 kW orV< 33 kVP>50 kW orV>33 kV

Odd, Non triplen

5126

78.55.1

114.32.2

1332.2

172.71.8

191.91.7

231.61.1

251.61.1

>250.8+0.8*25/n0.4

Triplen

316.67.5

92.22.2

150.60.8

210.40.4

> 210.30.4

Even

210.010

42.53.8

61.01.5

80.80.5

100.80.5

120.40.5

>120.30.5

Total20.0 %12 %

Page 1 of 2

IMPEDANCE, SHORT CIRCUIT CURRENTS,

AND VOLTAGE DISTORTION

General

This application note addresses the significance of the output impedance of a transformer to short circuit currents and voltage harmonic development on

the applied source. A quality transformer is made with copper coils wrapped around steel laminate. The coils characteristics

include resistance (R) and inductive reactance (X). The impedance (Z) is equal to the vector sum of resistance and inductive reactance.

Impedance

Impedance is the total current limiting factor ( i=e/z ). For transformers it is more convenient to rate the impedance as a

percentage than use its absolute value. Typical impedance is between 2% and 9%. At very low values of impedance (below 3%) a

correlation to efficiency can be established but there is no direct relationship because the resistance varies.

Fault Current

The purpose of investigating the impedance is the relationship to the transformers short circuit current (Isc) and the associated circuit breaker fault clearing capacity. According to the NEC, a circuit breakers rating must be at least 120% of its full rated current. In the following example, the circuit breaker ampacity is 1000amps (833 x 120%) with a minimum asymmetrical interrupt current (AIC) capacity of 16,666 amps. Had the output impedance been 3%, the AIC would be 27,757 amps; requiring a more

expensive circuit breaker but rendering a much more efficient system. Therefore, a high output impedance transformer requires a lower AIC circuit breaker, however, the compromise contributes to voltage distortion. The lower cost of the circuit breaker is minor in comparison to the cost to correct the voltage distortion.

SAMPLE with: KVA Rating = 300 Input Voltage = 208 Vac Z = 5% Full load current = 300 Kva *1000 208 3 = 833 Amps Isc = Short Circuit Current Isc = Full load current Impedance (Z) Isc = 833 .05 Isc = 16,666 Amps

Voltage Distortion

An economical balance must be obtained when considering the impedance. Lowering the impedance minimizes the voltage waveform distortion, typically lowering the K-rating and increasing the fault current. This is not a concern below 150 KVA,

however, above 150 KVA, an abnormally low impedance becomes costly and difficult to coordinate the protection devices. A good compromise is to incorporate K-rated transformers with an impedance of 3 to 4% and operate the transformer at less

than full capacity. This approach assists in achieving operation within specified limits defined by IEEE 519, Maximum Harmonic Current Distortion in % of Load Current (Table 10.3).

ukimpea1 6April1998

APPLICATION NOTES Ultra-K - UK#16

Page 2 of 2

The electrical distribution contains harmonic currents, with the 5th and 7th harmonic being predominant. They cause additional heating and produce a voltage distortion. The voltage distortion produced is related to the impedance (e = iz). In order to minimize the effects it is important to keep the impedance of the transformer low. IEEE 519 defines the acceptable Total Demand Distortion (TDD) for an individual harmonic order which is based on Isc/IL. (IL= actual load current)

Example: Case A Isc = 16,666 Amps @ Z=5% IL = 833 Amps 100% Isc/ IL = 20 Case B Isc = 27,575 Amps @ Z=3% IL = 833 Amps 100% Isc/ IL = 33 Case C Isc = 27,575 Amps @ Z=3% IL = 540 Amps 65% Isc/ IL = 51 From table 10.3 Maximum current harmonic distortion for individual harmonic orders less than 11.

Case A = 4% Case B = 7% Case C = 10% These cases demonstrate the need to keep the impedance low and refrain from full load current operation to minimize the harmonic current effects. K-rated transformers must be used in applications that involve harmonics to eliminate overheating. A prem-ium K-rated transformer, at or below 500 KVA, should have no more than 4% impedance and an efficiency of 98% or better.

Summary

Controlled Power Company manufactures the Ultra-K, a K-rated transformer with these conditions in mind. The output impedance is between 3% and 4%

with K-factors of K-4, K-7, K-13, and K-20. It is a multi-shielded isolation transformer, the only one in the industry with a pre-wired high frequency filter and TVSS. It

is designed for high harmonic current loads such as induction motors, welders, and mainframe computer networks.

Even Harmonics are limited to 25% of the odd harmonic limits. TDD refers to Total Demand Distortion and is based on the average maximum demand current at the fundamental frequency, taken at the PCC. * All power generation equipment is limited to these values of current distortion regardless of ISC / IL. ISC = Maximum short circuit current at the PCC IL = Maximum demand load current (fundamental) at the PCC h = Harmonic order

Table 10.3

ISC / IL