FLOMATCHER/MARATHON
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The rotor circuit voltage in a wound rotor motor is inversely proportional to speed, and torque produced is proportional to rotor current. Therefore, the speed of the motor can be held at a set point by regulating the rotor current (torque) so that it equals the torque required by the load. Regulation of the rotor current in the Wattmiser is accomplished by control of the firing angle of the inverter SCR's. Because the firing angle is continuously variable, the speed of the wound rotor motor is stepless and continuously variable. The Wattmiser regulator compares a speed reference signal with a rotor derived voltage feedback signal representing actual motor speed. The resulting error signal is fed into a current regulator which adjusts the firing angle of the SCR's to reduce the error signal to zero. This process balances motor torque with load torque at the set speed point. In addition, the current regulator is supplied with an inverter current feedback signal to limit the inverter current to a safe value. Control protective features include under-voltage, phase loss, instantaneous overcurrent, and inverse time overcurrent. The control is insensitive to incoming line phase rotation. |
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