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WorksheetsSemiconductors: Thyristors
Total questions: 15
Worksheet time: 16mins
A Silicon Controlled Rectifier is a (a) semiconductor device.
The SCR has three connecting terminals. These are the (a) .
(type answer as a list with spaces after the commas
e.g. cat, mouse, horse)
In its on state, current flows from the Cathode to the Anode of an SCR
True
False
In its on state, current flows from the Anode to the Cathode of an SCR.
True
False
The SCR has three modes of operation. These are
Forward conducting
Reverse Conducting
Forward Blocking
Reverse Blocking
The gate of Thyristors is usually connected to resistors. The reason for this is
to ensure the gate is always on
to limit the gate current
to get a spike in the gate signal
to filter out the noise in a circuit.
An SCR can be switch "on" by exceeding the forward breakover voltage from Anode to Cathode.
True
False
The SCR in this circuit has a maximum gate current rating of 50 mA. The gate-cathode voltage drop is 1V, this means there should be a (a) resistance to protect the gate.
Which of the following are advantages of using Thyristors?
They can handle large current, voltage and power
They can be used for AC and DC applications
The control process is simple
They are expensive
A Triode for AC can be used to control (a) of an AC input signal.
The SCR can be used to rectify all or some of an AC signal. This is achieved by
changing the polarity.
connecting the gate terminal to the cathode.
changing the signal input.
changing the delay firing angle
The gate of a TRIAC is used to
trigger it into reverse blocking mode.
trigger it into forward blocking mode.
trigger it into conduction.
trigger it into DC operation mode.
A TRIAC is configured to use 60% of the usable power from an AC source. What is the delay firing angle of this control process?
Ans: (a)
An AC input wave has a frequency of 40Hz. To use 50% of the wave a TRIAC is triggered _____ after the wave passes zero.
6.44 ms
25 ms
12.5 ms
6.25 ms
The TRIAC does not have an Anode and Cathode because it allows current to pass in both directions.
True
False
