Question 1

The SCR is a rectifier.

Accepted Answer

Yes, SCR stands for Silicon Controlled Rectifier which is a type of rectifier used to convert alternating current (AC) to direct current (DC).

Question 2

The amount of current required to keep the SCR turned on is called the ____.&#10;A) input current&#10;B) leaking current&#10;C) output current&#10;D) holding current

Accepted Answer

The amount of current required to keep the SCR turned on is called the holding current.

Question 3

To test an SCR, connect the negative output lead of the ohmmeter to the anode and the positive lead to the cathode.

Accepted Answer

To test an SCR, you need to use a special testing circuit or an SCR tester, not an ohmmeter. An ohmmeter cannot test the functionality of an SCR.

Question 4

The SCR is a member of a family of devices known as ____.&#10;A) gates&#10;B) rectifiers&#10;C) thyristors&#10;D) PNPNs

Accepted Answer

The SCR (Silicon Controlled Rectifier) is a type of thyristor, which is a family of devices that includes other types such as Diacs and Triacs. Therefore, the correct answer is C, thyristors.

Question 5

If the SCR is to control all of the positive waveform, it must be phase shifted.

Accepted Answer

An SCR can only conduct during the positive half-cycle of the AC waveform. To control the entire positive waveform, the SCR must be phase-shifted so that it turns on at the beginning of the positive half-cycle.

Question 6

One disadvantage of the GTO over a common SCR is its inability to control power in a direct current circuit.

Accepted Answer

GTOs (Gate Turn-Off thyristors) can control power in both alternating current (AC) and direct current (DC) circuits, similar to SCRs (Silicon Controlled Rectifiers), but with the added ability to be turned off by a gate signal, which is not a feature of common SCRs.

Question 7

SCRs designed to switch currents of ____ or more may indicate some leakage current when tested.&#10;A) 40 amperes&#10;B) 50 amperes&#10;C) 60 amperes&#10;D) 70 amperes

Accepted Answer

SCRs designed to switch currents of 50 amperes or more may exhibit some leakage current when tested, due to their larger junctions necessary for handling higher currents.

Question 8

When the AC waveform drops to 0 at the end of each half cycle, it will permit the SCR to ____.&#10;A) be rectified&#10;B) turn off&#10;C) stabilize&#10;D) turn on

Accepted Answer

When the AC waveform drops to 0 at the end of each half cycle, it will cause the SCR to turn off, as it requires a trigger pulse at the gate to turn on again.

Question 9

When touching the gate of the SCR to the anode, the ohmmeter should indicate ____ through the SCR.&#10;A) continuity&#10;B) leakage current&#10;C) polarization&#10;D) discontinuity

Accepted Answer

When touching the gate of the SCR to the anode, the ohmmeter should indicate continuity through the SCR indicating that the device is in a conducting state. A leakage current would indicate that the device is partially turned on, and polarization or discontinuity would indicate that the device is not functioning properly.

Question 10

The silicon-controlled rectifier (SCR) is made by joining four layers of semiconductor material together.

Accepted Answer

The SCR is made by joining three layers of semiconductor material together - an N-type layer, a P-type layer, and another N-type layer.

Deck 54: The Silicon-Controlled Rectifier and Gto