11-05-2013, 04:09 PM
Chopper-Controlled DC Motor Drive
Chopper-Controlled.pdf (Size: 236.05 KB / Downloads: 159)
• Chopper: The variable dc voltage is controlled
by varying the on- and off-times of a converter.
• Fig. 4.1 is a schematic diagram of the chopper.
• The duty cycle d can be changed in two ways:
(i) varying the on-time (constant switching
frequency).
(ii) varying the chopping frequency.
• Constant switching frequency has many
advantages in practice.
Model of The Chopper
• The transfer function of the chopper is
where Kr = Vs/Vcm, Vs is the source voltage,
and Vcm is the maximum control voltage.
• Increasing the chopping frequency decreases
the delay time, and its becomes a simple gain.