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What do you mean by latching current?
Latching current can be defined as it is the least amount of anode current which is necessary to supply from the anode terminal to the cathode terminal to activate the SCR after detaching the gate terminal. This is allied with the turned-off method.
How is latching current measured?
The value of the latching current IL is the value of the IT current read as soon as the triac re- mains on, after suppressing the gate current IG. Only sensitive thyristors (IGT ≤ 500µA) are measured with a 1 KΩ resistor between gate and cathode.
What is meant by latching current and holding current?
Latching current of forward biased SCR is the minimum current which anode current must attain to continue to remain in forward conduction mode even when gate current is removed. Holding current of SCR or thyrsistor is that minimum value of current below which anode current must fall to come in OFF state.
What is meant by TRIAC?
A TRIAC (triode for alternating current; also bidirectional triode thyristor or bilateral triode thyristor) is a three terminal electronic component that conducts current in either direction when triggered. The term TRIAC is a genericised trademark.
How do you do SCR?
This extra terminal is called the gate, and it is used to trigger the device into conduction (latch it) by the application of a small voltage. To trigger, or fire, an SCR, voltage must be applied between the gate and cathode, positive to the gate and negative to the cathode.
When does the latching occur on a TRIAC?
The gate current that effectively latches a triac is the latching current and is given as LT. The latching can happen when the load current has reached the LT value, only after this the latching enables even while the gate current is removed.
How does the next circuit work with TRIACs?
The next circuit is another version of a triac based timer. When switched ON, the UJT is switched via the 100uF capacitor. The UJT keeps the SCR switch OFF, depriving the triac from the gate current, and thus the triac also remains switched OFF.
What is the trigger voltage of a TRIAC?
The trigger voltage applied across the gate and the A1 terminal of a triac is referred to as VGT. It is applied through a resistor which will discuss shortly. The gate current that effectively latches a triac is the latching current and is given as LT.
What can a TRIAC flasher circuit be used for?
This triac flasher circuit can be used to flash a standard incandescent lamp with a frequency that may be adjusted between 2 and about 10 Hz. The circuit works by rectifyingthe mains voltage by a 1N4004 diode along with an variable RC network.