Question

How output voltage of chopper can be varied?

(a) By using constant frequency system

(b) By using variable frequency system

(c) By using constant and variable frequency systems

(d) By using constant or variable frequency systems

I had been asked this question in an online interview.

My question is based upon DC Motor Control Through Choppers topic in portion Motor Control by Static Power Converters of DC Machines

Answer 1

Right choice is (c) By using constant and variable frequency systems

To elaborate: The average voltage of the chopper output depends on α, thus, α can be varied by either changing the complete time period or by changing an on time or off time. These two methods are named as constant and variable frequency system.