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DESIGNING ENERGY EFFICIENT SYSTEMS
Presented by: Jon Rhodes
CFC-Solar, Inc [email protected] Sponsored by:
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ENERGY EFFICIENT DESIGN
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ENERGY EFFICIENT DESIGN
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ENERGY EFFICIENT DESIGN
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ENERGY EFFICIENT DESIGN
• Oversized motors operating on light loads normally have low efficiency.
• Heat buildup in a motor at a 50% overload is not much more then it is under normal operating conditions.
• If a hydraulic system has fluctuating load requirements, working a smaller horsepower motor harder than a larger motor usually results in improved overall efficiency and power factor.
• This also reduces operating costs, size and weight.
RMS Horse power Calculations
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RMS HP = HP1² x t1 + HP2² x t2 + ……… t1 + t2 + ……... Charting Step HP HP² Time sec HP² x Sec 1 3 9.0 3 27.0 2 7.5 56.3 10 563.0 3 2.5 6.3 12 75.6 4 12.5 156.3 3 468.8 Totals 28 1134.4 Divide 1134.4 by 28 then take the square root = 6.4 HP
ENERGY EFFICIENT DESIGN
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• Next, check the breakdown torque for the next higher motor offered as a standard. In this case consider a 7½ HP motor,( 80 ft. lbs.)
• Divide the breakdown torque by the full load operating torque of that motor times 80%.
• Example: 80 ft. lbs. / 20 ft. lbs. x .80 = 3.20 or 320% • Then take the maximum HP calculated on your chart
and divide by the motor HP from the RMS formulae times 100 gives the minimum breakdown torque required. This must be less then calculated above.
• Example: 12.5 / 7.5 x 100 = 167% • The 7 ½ HP motor would be more than adequate.
ENERGY EFFICIENT DESIGN
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• Using “Service Factors” of electric motors. – Amount over the rated name plate horse
power listed on motor that the motor may be loaded continuously and still carry full warrantee from Mfg.
– Standards 1.00, 1.05, 1.10, 1.20, 1.30 – Example: 10 hp with SF 1.3 = 13 HP – Heat buildup in a motor at a 50% overload is
not much more then it is under normal operating conditions.
ENERGY EFFICIENT DESIGN
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ENERGY EFFICIENT DESIGN
Bias Spring High pressure spring
(X)
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Compare pressure drop across directional valve with a P to T spool to that of a vented pressure relief valve
ENERGY EFFICIENT DESIGN
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ENERGY EFFICIENT DESIGN
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Orifice
Load Sense Compensator Spool
Stand-by 200 PSI pressure setting
LOW PRESSURE STAND-BY
ENERGY EFFICIENT DESIGN
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800 PSI
600 PSI
200 PSI spring AND 600 PSI Hyd pressure
800 PSI
Pump de-strokes to limit pressure
ENERGY EFFICIENT DESIGN
Load sensing at lower pressure
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High Pressure Compensator Spool
Maximum Allowable Pressure
200 PSI spring AND 3000 PSI Hyd pressure
3000 PSI
ENERGY EFFICIENT DESIGN
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EM
Gage A
Sol. 1A Sol. 1B
3000 PSI
Set Max Compensator to 2700 PSI
Set Load Sense to 300 PSI
Gage C Gage B
Spool selected provides stand-by pressure when in neutral
Using a true servo flapper type pilot saves 1 to 2 amps of power draw when shifting valve. However, the heat generated by the pilot valve must be considered.
ENERGY EFFICIENT DESIGN
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ENERGY EFFICIENT DESIGN
Pressure 0 1000 3000
Flow
0
20
40
High flow until reducing valve setting is reached, then load sense across flow control
Flow control can be a proportional valve of a much smaller size.
Load sense spring setting (PSI) should be adjusted to match the max controlled flow with the flow control fully opened for good resolution.
Directly operated non-relieving reducing valve
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HORSE POWER/TORQUE LIMITING PUMP
• This feature allows maximum flow up to a pressure that results in reaching the maximum horse power available.
• Pressure above can continue increasing but the flow rate will drop proportionally.
• Example: doubling the pressure will result in half the maximum flow.
• Requires a pressure compensator limiter to control final maximum pressure.
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Maximum compensator PSI
High speed
Maximum limit of Electric motor HP
Horse power / torque limiter control
Pressure
Flow
Flow decreases at same rate PSI increases Maintaining max HP limit
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Maximum compensator PSI
High speed
Maximum limit of Electric motor HP
Horse power / torque limiter control with load sense and pressure reducing valve
Pressure
Flow
Flow decreases at same rate PSI increases Maintaining max HP limit
ENERGY EFFICIENT DESIGN
Load sense flow control for varying speeds
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ENERGY EFFICIENT DESIGN
Things that can affect the efficiency of systems – Conductor sizes and avoidance of elbows. – Use a single pump of correct flow for each actuator. – Variable speed electric motors with fixed volume
pumps. – Avoid flow controls. – Avoid pressure reducing valves. – Weighted fly wheel for additional peak force.
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ENERGY EFFICIENT DESIGN
Sizing considerations for efficient systems – Electronic Control Interaction with other Systems – Use increased controls data to precisely match load
demands with hydraulic HP usage – Maximum and Minimum required flow and pressure
conditions – Power to Weight Ratios – Use Accumulators for overall HP reduction
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ENERGY EFFICIENT DESIGN
