TNA-Motor

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Motor Maintenance and TestingMotor Maintenance and Testing

Presented By.Presented By.

Muhammad BilalMuhammad Bilal

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MotorMotor

Motor converts electrical energy toMotor converts electrical energy tomechanical energy.mechanical energy.

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Motor ConstructionMotor Construction

The StatorThe Stator

The stator forms a hollow cylinder with coils ofThe stator forms a hollow cylinder with coils ofinsulated wire inserted into slots of the stator core.insulated wire inserted into slots of the stator core.

The coils, plus the steel core form the electromagnets.The coils, plus the steel core form the electromagnets.

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Motor ConstructionMotor Construction

The RotorThe Rotor

There are two types of motor rotors:There are two types of motor rotors:

The wound rotorThe wound rotor

The squirrel cageThe squirrel cage

The wound rotor has coils of wire wound in the slots ofThe wound rotor has coils of wire wound in the slots ofthe rotor (Similar to generator coils).the rotor (Similar to generator coils).

The Squirrel cage consists of bars of copper orThe Squirrel cage consists of bars of copper oraluminum electrically connected at each end withaluminum electrically connected at each end withconducting rings.conducting rings.

As the rotor rotates inside a magnetic field, it receivesAs the rotor rotates inside a magnetic field, it receiveselectromagnetic induction, then current flows and formelectromagnetic induction, then current flows and formthe rotor electromagnetthe rotor electromagnet..

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The RotorThe Rotor

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IP RatingsIP Ratings

An international classification system forAn international classification system forthe sealing effectiveness of enclosures ofthe sealing effectiveness of enclosures of

electrical equipment against the intrusionelectrical equipment against the intrusioninto the equipment of foreign bodies (i.e.into the equipment of foreign bodies (i.e.tools, dust, fingers) and moisture. Thistools, dust, fingers) and moisture. Thisclassification system utilizes the lettersclassification system utilizes the letters

"IP" ("Ingress Protection") followed by two"IP" ("Ingress Protection") followed by twoor three digits.or three digits.

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Direction of rotationDirection of rotation

The direction of rotation of an inductionThe direction of rotation of an inductionmotor depends on the phase sequence ofmotor depends on the phase sequence of

the supply voltage. If we change thethe supply voltage. If we change thephase sequence then the direction of thephase sequence then the direction of themotor changes.motor changes.

R Y BR B Y

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SlipSlip

Difference between speed of magnetic field ofDifference between speed of magnetic field ofstator and rotor speed.stator and rotor speed.

S = NsS = Ns NrNr

%S = (Ns%S = (Ns--Nr)/Ns x 100Nr)/Ns x 100

Ns = Synchronous speedNs = Synchronous speed

Nr = Rotor speedNr = Rotor speed

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Motor trouble shooting chartMotor trouble shooting chartSYMPTOMSYMPTOM CAUSECAUSE REMEDYREMEDY

Motor fails to startMotor fails to start

Defective power supplyDefective power supply

a) Blown or defective fusesa) Blown or defective fuses

Check voltage across allCheck voltage across allphases.phases.

2. Open control circuit2. Open control circuit

a) overload trips or open.a) overload trips or open.

b) Loose or poor connection inb) Loose or poor connection incontrol circuit.control circuit.

Push reset button ofPush reset button of

bimetal relay.bimetal relay.

3. Sensing element (cold type)3. Sensing element (cold type) Make visual inspection ofMake visual inspection ofconnections in motorconnections in motorterminal box and in controlterminal box and in controlpanel.panel.

4. Tripping device not properly4. Tripping device not properlyconnected.connected.

Check connections withCheck connections withdiagram given in motordiagram given in motorcontrol Unit.control Unit.

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SYMPTOMSYMPTOM CAUSECAUSE REMEDYREMEDY

Motor fails to comeMotor fails to comeup to speedup to speed

1. Low or incorrect1. Low or incorrectvoltage.voltage.

Check voltage on all phases inCheck voltage on all phases incontrol panel and at motorcontrol panel and at motorleads.leads.

2. Incorrect connection2. Incorrect connectionat motor terminals.at motor terminals.

Check for proper leadCheck for proper leadconnection at motor. Compareconnection at motor. Comparewith connection diagram.with connection diagram.

3. Mechanical overload.3. Mechanical overload. Check impeller setting. CheckCheck impeller setting. Checkfor a locked or tight shaft.for a locked or tight shaft.

4. Hydraulic overload.4. Hydraulic overload. Check impeller setting. CheckCheck impeller setting. Checkgallons/minute against pumpsgallons/minute against pumpscapacity and head.capacity and head.

Motor trouble shooting chartMotor trouble shooting chart

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Motor runs hotMotor runs hot

1. Inadequate ventilation1. Inadequate ventilation Assure adequate supply of freshAssure adequate supply of freshair. Check air blast through motorair. Check air blast through motorby feeling air discharge atby feeling air discharge atventilating ducts.ventilating ducts.

2. Overload2. Overload Check load with ammeter.Check load with ammeter.

3. Unbalance supply3. Unbalance supplyvoltage.voltage.

Check supply voltage on allCheck supply voltage on allphases. Check to be made bothphases. Check to be made bothwith motor running and at rest.with motor running and at rest.


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Bimetal overload tripsBimetal overload tripsduring start.during start.

1. Wrong bimetal relay1. Wrong bimetal relaysetting.setting.

Set thermal overload relaySet thermal overload relaycorrectly.correctly.

2. Voltage drop on load.2. Voltage drop on load. Check incoming supply.Check incoming supply.Lead wires of greaterLead wires of greatercross section may becross section may be

requiredrequired


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Bimetal relayBimetal relaytrips duringtrips duringoperation.operation.

1. Overload1. Overload Check load with ammeterCheck load with ammeter

2. Voltage drop.2. Voltage drop. Check incoming supply. Lead wiresCheck incoming supply. Lead wires

of greater cross section may beof greater cross section may berequired.required.

3. High temp. in pump3. High temp. in pumphouse or control.house or control.

Check the temperature with aCheck the temperature with athermometer and compared withthermometer and compared withpermissible ambient temperature.permissible ambient temperature.

4. Ventilation ducts partly4. Ventilation ducts partlyclosed.closed.

Remove foreign particles and cleanRemove foreign particles and cleanthe ductsthe ducts

5. Ventilation ducts5. Ventilation ductsinsufficient.insufficient.

Increase duct area.Increase duct area.


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Bearing overheatBearing overheat

1. Too much grease in1. Too much grease inbearings.bearings.

Remove extra greaseRemove extra grease

2. Loss of lubricity (old2. Loss of lubricity (oldgrease)grease)

ReRe--grease.grease.

3. Improper alignment.3. Improper alignment. Realign and couple.Realign and couple.


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Motor vibratesMotor vibrates

1. Head shaft misaligned1. Head shaft misaligned Realign and couple.Realign and couple.

2. Worn line shaft bearings or2. Worn line shaft bearings orbent line shaft.bent line shaft.

Disconnect motor from pump andDisconnect motor from pump andrun motor without load torun motor without load todetermine source of vibration.determine source of vibration.

3. Hydraulic disturbance in3. Hydraulic disturbance inpump column or dischargepump column or dischargepipe.pipe.

Check proper setting andCheck proper setting andalignment of pump dischargealignment of pump dischargehead and discharge pipe.head and discharge pipe.


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Motor noisyMotor noisy

1. Electrical noise.1. Electrical noise. Most motors are electrically noisyMost motors are electrically noisyduring the starting period. Thisduring the starting period. Thisnoise should diminish as motornoise should diminish as motorreaches full speed.reaches full speed.

2. Single2. Single--phasing of supply.phasing of supply. Check voltage on all phases inCheck voltage on all phases incontrol panel and at motor leads.control panel and at motor leads.

3. Mechanical or hydraulic overload.3. Mechanical or hydraulic overload. Check impeller setting. Check forCheck impeller setting. Check fora locked or tight shaft.a locked or tight shaft.

Check impeller setting. CheckCheck impeller setting. Check

gallons/minute against pumpsgallons/minute against pumpscapacity and head.capacity and head.

4. Worn bearing4. Worn bearing

a)a) Bearing has foreign particlesBearing has foreign particlesinside or dirty.inside or dirty.

b)b) Bad surface of bearing ringsBad surface of bearing rings

or bearing balls.or bearing balls.

Motor to be dismantled bearingsMotor to be dismantled bearingsto be washed and visuallyto be washed and visuallyexamined.examined.

Bearings must be replacedBearings must be replaced


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