Running a 380V motor on a 440V power supply (at increased voltage) will bring up a few problems:
- Increased voltage drop while starting will probably make lights flicker.
- The starting and maximum torque will be increased resulting in a possible shearing of the coupling.
- Starting currents will be higher.
- Increased motor current at same power will cause over-heating.
- Ageing of insulation will be accelerated due to over-heating.
- The power factor will be low.
The economic loss from premature motor failure is devastating. In most cases, the price of the motor itself is trivial compared to the cost of unscheduled shutdowns of processes. Both high and low voltages can cause premature motor failure, as will voltage imbalance. Here, we’ll look at the effects of low and high voltage on motors and the related performance changes you can expect when you use voltages other than those noted on the nameplate.
Can cooling help?
The one thing you can take into account is cooling. The motor will be specified at a certain ambient free flow air environment. If you can increase the air-flow over the rotor or otherwise extract heat from the core, you can in fact drive the motor harder with little significant effect on the motor other than reduced brush life.