Speed Controller Design
It is necessary to design the speed controller next. To design the speed
controller, it is necessary to represent the transfer function G2(s)
suitably. It is found that for a wide range of values, two of the zeros of
G2(s) are located near two of the poles and the other two poles
are away from the origin. Hence while designing the speed loop, G2(s)
is set equal to unity. The simulation of the drive presented later would show
whether this simplification is justified.
The design of the speed controller is carried out based on the assumption
that the motor is on no load. A variable drive system tends to exhibit oscillatory
behaviour under no load conditions and hence the design based on no load condition
is assumed to be justified. Here the output of the speed controller is not
clamped, whereas there would be limits on the output of speed controller.
The output of speed controller corresponds to armature current and it is necessary
to limit the peak value of speed controller in order to protect the SCRs used
in the bridge. The applet presented later for simulating the drive has limits
imposed on the output of the speed controller.
click here to open the applet
TO THE TOP |
