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Operating Electric Motors

Find the horsepower rating on the nameplate of the motor.  Multiply kilowatts (kW) of corresponding horsepower on the chart by the total number of hours the motor is used. This figure - kilowatt-hours (kWh) - multiplied by the applicable rate, will give you the cost of operation.

Example:

How much would it cost to operate a 10 h.p. motor 24 hours per day for three weeks?

10 H.P. 230V 1Ø, 24 hours/day for 3 weeks.

ANSWER: (assuming the electric rate is $.08)

8.625 kW x 24 hours x 21 days = 4,347 kWh
4,347 kWh x $.08 = $347.76

Note: No capacity charge included.

Squirrel cage motors with average efficiency
and power factor for each size
1Ø = Single-Phase; 3Ø= Three-Phase 

H.P. 115 V 10 kW
@ Full Load<
230 V 10 kW
@ Full Load
230 V 30 kW
@ Full Load

1/6 

.329  .329   
¼  .447  .447 
1/3  .571 .571
½  .800  .800  .568
¾  1.159  1.159  .774
1 1.380  1.380  .999
1 ½  1.794  1.794  1.335
2.180  2.180  1.893
3 3.167 3.167 2.868
5   4.701  4.478
7 ½ 6.808  6.310
10   8.625  8.724
15      12.269
20  16.679
25    20.197
30    24.858
40    33.044
50 38.752
60 48.078
75    60.105
100   82.253
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