Motor related Help?

Question

Is 3 phase AC induction motor specified in terms of Voltage, Current & Power. I have heard that a motor can be operated over a range of volt, current & power. then what do the rated values indicate. Also if a motor is specified as 48 V AC, 300A then can it be operated with a battery that could supply 48V DC... neglect all the losses & the need for an alternator. Thanks in advance...

Answer 1

The numbers on the nameplate are the maximum recommended operating voltage, and the nominal operating frequency, and with that voltage, frequency, and the rated load, the current and power you would see being used by the motor.

Most motors if you reduce the voltage, they will operate at a slower speed, and will draw lower amounts of current and power, but exactly what will happen depends on the motor type.

You cannot operate a AC motor on DC.

Answer 2

Motor data is usually Full Load data, that being the current it will draw when the motor is loaded at maximum.

The voltage can vary by 5% typically some by as much as 10%. This may also be noted on the Data Name Plate.

A 3ph AC motor cannot run on a DC source.

The rating of 48VAC, 300A is suspect. Are you sure it is not 480VAC, 300A? The 480VAC 3ph motor is common here in the US.

Answer 3

The rated voltage is nominal voltage for which the motor is designed. The voltage can vary by plus or minus ten percent or so and the motor will still deliver the rated power without overheating so much that its useful life will be significantly shortened.

The rated power is the power that the motor can deliver to the load 24 hours per day, seven days a week at rated voltage and rated ambient temperature for its expected lifetime. If the load is a little higher the motor's life will probably not be effected too much particularly if the temperature is not always at the maximum. If the load is less than the rated power, the motor will probably last longer than expected. The power delivered will be only what it takes to drive the load, so it can be much less than the rated power, but the motor will be less efficient if the load is a lot less than the rated power.

The rated current is the current that the motor draws when it is operating at the rated voltage and delivering the rated power. If the voltage and/or load are above or below the rated values, the current will be above or below the rated value. Over a small range of voltage variation, the current changes in the opposite direction as the voltage change so that voltage multiplied by current will be about constant.

Any battery of any voltage and sufficient power delivery capability could supply power provided that the DC power is converted to an AC voltage and frequency that are appropriate for the motor.