What type of protection is obtained from a circuit breaker having the following trip unit: no trip unit?
None
100
What type of protection is obtained from a circuit breaker having the following trip unit: thermal-mag.?
short circuit and overload
100
What are three common diode ratings?
Forward current, peak inverse voltage, and watts
100
A three phase half wave recitifier produces what type of output?
pulsating DC
DC = .675 x AC
100
What are SCRs commonly used for in mining machinery?
control speed
200
What type of protection is obtained from a circuit breaker having the following trip unit: shunt trip?
Remote tripping
200
Who should test circuit breakers, and how often should they be tested?
Tested by a certified electrician designated by the operator as often as necessary not to exceed monthly
200
What is the forward voltage drop across a silicon diode?
approximately .6 volts
200
A Three phase full wave rectifier produces what type of output?
Pulsating DC
DC = 1.35 x AC
200
What do we call the amount of time and SCR is turned on ?
conduction angle
300
What type of protection is obtained from a circuit breaker having the following trip unit: magnetic?
Short circuit
300
A zero reading in one direction and an infinity reading in the other direction on an ohmeter connected across a diode indicateds what condition?
Good
300
What is the forward voltage drop across a germanium diode?
.25 volts
300
What do the initials SCR stand for?
Silocon controlled rectifier
300
Will an SCR conduct in both directions once it is turned on?
NO
400
What type of protection is obtained from a circuit breaker having the following trip unit: undervoltage?
undervoltage
400
A single phase half wave recitifer produces what type of output?
Intermittent pusating DC
DC = .45 x AC
400
What is A zero ohmeter reading in both directions across a diode would indicate what condition?
shorted
400
How is an SCR turned on?
A positive pulse with respect to the cathode applied to the gate
400
What reading should be obtained on an ohmeter when the negative lead is connected to the cathode and the positive lead is connected to the anode on a good SCR that has not been fired?
What reading should be obtained on the ohmeter when the leads are reversed?
Infinity
Infinity
500
What type of protection is obtained from a circuit breaker having the following trip unit: thermal unit
overload
500
A single phase full wave recitifier produces what type of output?
Pulsating DC
DC = .9 x AC
500
An infinity reading in both directions across a diode indicates what condition?
open
500
What are two methods that may be used to turn an SCR off?
Drop current below the holding current value or
Reverse vias the cathode anode junction
500
If infinity readings are obtained on an ohmeter does this prove that the SCR is good?
If yes, how? If no, what other test should be performed?