using differential movement of the two motors, e.g. using differential gearboxes

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Arrangements specially adapted for regulating or controlling the speed or torque of two or more electric motors (H02P6/04, H02P8/40 take precedence) > for speed regulation of two or more dynamo-electric motors in relation to one another > by comparing mechanical values representing the speeds > using differential movement of the two motors, e.g. using differential gearboxes