Ward-Leonard system

One of the oldest adjustable-speed drives is the Ward-Leonard system. This consists of an ac to dc motor-generator set and a shunt or compound-wound dc motor. Speed is adjusted by changing the generator voltage. A functional equivalent of this drive uses an adjustable-voltage rectifier feeding a dc motor. This system has only one rotating machine in contrast to the three of a conventional Ward-Leonard system. 

Ward Leonard speed control system for sodium pumps was improved by eliminating pump drive trip parameters, improve speed control accuracy to 1 ipm and working enAdromnent by providing air conditioned enclosures for the control panels. 

Depending on its size, the electric excavator is equipped with one or more motors. In the latter case, there is often a separate motor for crowding, slewing, lifting and travelling. On large machines, loss-free control and favourable starting conditions are provided by Ward-Leonard or thyristor systems. Otherwise rheostatic control is the usual method. 

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