P-MOVOC device

The P-MOVOC device is supplied as a necessary complement of the range of advanced frameless PM series TK motors when a constant power range in excess of 3:1, and up and beyond 1:10, is planned for the application. The special design and manufacturing technology of high speed TK motors allows a very wide constant power, flux controlled operating range which can exceed the ratio 10:1.

This means that the motor back EMF is approximately equal to the drive maximum voltage (typically very close to the supply voltage) at the motor knee speed, i.e. at the lowest speed of the constant power range. In normal operation, at higher speeds the drive feeds the motor, which is designed to display a calibrated, critical amount of impedance, with just the right amount of Id to keep the motor voltage constant throughout the constant power range.

This means that at the highest permissible speed the motor back EMF is higher than the supply voltage, intrinsically the back EMF is about equal to the supply voltage times the constant power range. As a consequence, without a voltage controller device, if the drive were to stop supplying Id to the motor when operating in flux control mode, a high voltage would be fed to the motor terminals. The vantage controller is thus added to the motor circuit to prevent any such occurrence. The voltage controlled device is connected between drive and motor, enerally and preferably near the drive.

If, for any reason, the drive were to stop supplying Id to the motor while operating at high speed, the voltage controller would detect the voltage rise and trigger a crowbar short circuiting all motor terminals so that the voltage across the motor is nullified and the current in the device is the short circuit current of the motor.

In turn, the short circuit current of high speed motors is very close to the nominal motor current. The motor would then idle down with high current but relatively little braking power. The motor voltage controller operates with or without power supply and only clears the motor short when the motor is completely stopped.