
4
D.C. MOTOR DRIVES
INTRODUCTION
In terms of numbers of installations, the controlled rectifier
(Thyristor') drive remains by far the most important form of
general purpose industrial drive, so we consider it first, and
in some depth. Later, we will look briefly at chopper-fed
drives which are used mainly in the medium and small sizes,
and finally turn attention to small servo-type drives.
THYRISTOR D.C. DRIVES
The overall arrangement of a drive intended to provide
closed-loop speed control is shown in Figure 4.1.
3-phase
Figure 4.1 Schematic diagram of speed-controlled d.c. motor drive
Speed
Ref.
Control
& Firing