DC Voltage Transducer delivers an output voltage proportional to the armature voltage or induced voltage. The output signal is mathematically isolated from the input voltage. The armature current signal is used to compensate the output signal for armature current variations in such a way that the output signal is approximately proportional to the induced EMF.
Where accurate EMF measurement is required, the measuring circuit also has an input which may be connected to the terminal of the machine. The voltage drop across the commutation winding of the machine is then used for IR compensation, and this arrangement therefore compensates to a considerable degree for the dependence of winding resistance on temperature.
Both static and dynamic voltage drop can be compensated by using both compensation inputs at the same time.
The unit is used for voltage control, where it replaces the tacho generator of the machine. The output signal is used as the actual value for the speed control system.
The unit is also used together with a field supply for controlled field current, in order to obtain automatic field weakening. The unit is connected at the factory for automatic field weakening if a controlled field exciter is ordered: if not, it is connected for voltage control.
