test voltage differs from nameplate

[fledge]

I've got a motor designed for 575VAC/3ph/60Hz that I want to test, but I only have a 460VAC/3ph/60Hz supply. If the nameplate fla of the motor at 575VAC is 1.6A, should I expect to see a test fla of 1.6A(575/460) = 2A, and size my test fuses as such? Thanks in advance for any help I get.

 

[jbartos]

Suggestion: Such test is not recommended since it would harm the motor, e.g. thermally at full load.
It is better to rent an autotransformer and test it at the motor rated voltage depicted on the motor nameplate.

 

[busbar]

On page 7 in

http://www.jeffersonelectric.com/pdf/3-phaseencap.pdf,

a simple 3ø open-delta 480-600V autotransformer set can be fashioned with a pair of off-the-shelf 240 X 480—120/240-Volt 1ø transformers.

 

[aolalde]

What kind of test do you have in mind?

No load test could show you that the motor is in good condition. You could do this test with lower voltage but the measured current will be the no-load current (magnetizing current +no load Losses). You will see integrity of the windings and mechanical condition (vibration).

Calibration test or temperature rise will require a dynamometer and nominal voltage supply.
Most of the manufacturing standards ask for 10% below of nominal voltage (517.5V) satisfactory operation. If the mechanical power demand is full load, the current will increase from the nameplate value inversely proportional to the voltage, to the change of efficiency (EFF) and power factor (PF). Excessive low voltage overheats the windings due to the current increase.

I = HP*746/(V*EFF*PF) (for single phase motors)

I = HP*746/(1.732*Vll*EFF*PF) (for three-phase motors)

Were HP is the power demanded by the load (at shaft extension) in Horse Power.
Vll = the line to line voltage of a three-phase circuit
V = Single phase voltage for 1 phase motors.