Electrical Engineering ⇒ Topic : Synchronous or rotary converter

SYNCHRONOUS OR ROTARY CONVERTER

A synchronous or rotary converter is a single machine with one armature and one field.It combines the function of a synchronous motor and a D.C. generator. It receives alternating current through a set of slip-rings at one end of an armature that rotates at synchronous speed, and delivers direct current from the opposite end through a commutator and a set of brushes.The principle of operation of a synchronous converter is based on the fact that an alternating e.m.f is induced in the armature of a D.C. machine and is rectified only by means of a commutator; therefore, when the armature winding is connected directly to slip-rings, an A.C. voltage is obtained across the rings, and the machine may be connected through the latter to an A.C. circuit.

Normally, a synchronous or rotary converter is used when a large-scale conversion from A.C. to D.C. power is required

                                                        Fig. (a) shows the main parts of a synchronous converter

                                                                              Fig. (a). Synchronous converter

Note. For machines whose output is less than 100 kW it is the usual practice to adopt a wave winding.When wave winding is used, only one connection is required per slip-ring. But when lap, or multiple circuit, wining is adopted, then each slip-ring will have connections equal to the number of pole pairs. A simple rule to remember is that ¿fa converter has N number of phases, there must be N slip-ring tapping points per pole pair.This rules does not apply to single-phase machines.