You purchase a motor in Germany designed to run at 415Volts, 50 Hz. It has 37.5 kW output power, runs at 2978 RPM and has 120 N-m of rated torque. You ship it Canada and run it at 460 Volts, 60 Hz. What will be the new speed in RPM? (Type in an integer.)
Answers
Explanation:
A motor is designed to work at a certain voltage and frequency, and its RPM is decided by its number of poles and frequency. Design allows for a variation of 10% on either side of design voltage.
Now a motor at 415 V 50 Hz will accept maximum 455 V AC at 50 Hz. It cannot accept 480 V and will fail over time even at 50 Hz.
On top of it, you suggest a frequency of 60 Hz. This will change the RPM in direct proportion. The motor parameters will not accept this big change. Apart from a higher RPM of nearly 3600, its fan, cooling, bearings will get affected. Output power permissible will be much lower, limited by current carrying capacity of its winding wires and heating in different points in motor.
However, the motor will fail in short period due to higher voltage levels and consequent degradation of insulation.
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