Basic DC Drives

SCR

A ( n ) . is a semiconductor switching device used to convert AC voltage into DC .

UJT

A ( n ) is a special type of transistor designed specifically to produce the triggering pulses for an SCR .

pulse

A ( n ) transformer is a special transformer designed for voltage pulses .

current flow in only one direction

A basic rectifier allows

variable resistor

A simple method of controlling the firing angle of an SCR is to connect a ( n ) _ across the anode and gate .

two

A single - phase full - wave rectifier will output DC pulse ( s ) during each cycle of the AC sine wave .

gate

An SCR is made up of an anode , a cathode and a

firing angle

Controlling the time at which the gate of an SCR goes positive with respect to the cathode is called adjusting the

Regenerative

DC drives are required for applications where high - inertia loads are repeatedly started and stopped .

2

During quadrant operation , the motor drives the load in the forward direction until reverse regeneration occurs , slowing the load .

average DC voltage

In rectification , the greater the number and duration of the pulses , the higher the will be .

Fixed - Resistance Timing Circuit

Which of the following is not a common SCR timing circuit ?

half - wave

rectification converts the AC sine wave input into a pulsating DC output at the same frequency .

Full - wave

rectification converts the AC sine wave into a pulsating DC output at twice the frequency .

RC network

timing circuits do not supply stable control of the firing angle because they are affected by temperature variations and other outside forces .