Three Phase Motor Measurement

The readings must be taken when the motor is operating at full speed, if there is a variable frequency drive, make sure is at 60hz

What is the approximate load on a three phase motor ?

This may be determined by taking an amperage reading while the motor is operating, and all three phases should be checked.

If the voltage is approximately the same as the rated voltage of the motor, and the ammeter is showing that the motor is drawing amperage is close to the nameplate reading, then the motor is carrying a full load.

If the amperage reading is less, the motor is not carrying a full load.

If the amperage is higher, then the motor is over loaded.

Example

Is it less expensive to operate a motor on 240 Volts AC or 120 Volts AC ?

The unit of electricity that we pay for is the WATT.
We currently pay .08004 cents per Kilowatt hour.
(1000 watts expended in 1 hour). 746 watts = 1 horsepower.

A 100 watt light bulb, on for 10 hours will expend 1000 watts of energy, costing .08004 cents for 10 hours of operation.

If I run a motor on 120 volts, and it draws 15 amps, then it will use 1800 watts per hour. 18,000 watts for 10 hours, 18 KWH = $ 1.44 for 10 hours.

That same motor can be hooked up to 240 volts, and then it only draws 7.5 amps ! But I x E still equals 1800 watts. So for 10 hours, it will still expend 18,000 watts, 18 KWH = $1.44 for 10 hours.