What is the minimum current to activate a TRIAC?
TRIode for Alternating Current
A TRIAC (TRIode for Alternating Current) is an electronic component that either allows electrical current to pass or stops it. It can be compared a bit to a light switch. The difference is that no manual action is required, but an electronic signal is required to activate the TRIAC. But that alone is not enough. The current flowing through the TRIAC must be sufficient, otherwise the TRIAC will not remain activated.
When a small electrical load (such as an LED light) is connected to a TRIAC controller, nothing will happen. When the TRIAC is activated, the electrical current will not be sufficient to activate the TRIAC.
Therefore, to test an electronic fan speed controller, a larger load is required. As a rule of thumb, the load must be at least 10% of the nominal current. A fan speed controller for motors up to 1,5 A can therefore be tested with a load that consumes at least 0,15 A. By connecting such a load to the electronic fan speed controller, it can be checked whether the controller is functioning correctly.
Phase Angle Control
Electronic fan speed controllers use TRIACs to cut chunks out of the supplied supply voltage. In this way they reduce the voltage supplied to the motor. By lowering the motor voltage, the motor will run slower. This technology is called Phase Angle Control.
The advantage of electronic fan speed controllers is that the motor speed can be infinitely adjusted. The controller itself operates completely silently. At lower speeds, engine noise may increase because the supplied supply voltage no longer has a perfect sinusoidal shape.