I have an air compressor I'm trying to troubleshoot and I'm trying to determine if the problem is with a small circuit board with a triac. The board takes as input an ac wall outlet (US) and outputs to a motor. The triac is a BTA24 600BW (datasheet: http://www.st.com/web/en/resource/technical/document/datasheet/CD00002264.pdf).
I understand how using a triac as a switch works but this triac is used to control motor speed so it is using phase control which I have zero experience with. How do you measure/test the output of a triac using phase control? I've got two multimeters and one shows output of 0 volts while the other shows 110 volts. The one showing voltage is a more expensive meter so I'm not sure if it is just more sensitive or picking up some slight current leakage that the other isn't or if the phase control stuff is throwing the meters off.
Can you use a multimeter to measure the output of a triac which is being used for phase control? If so, how? And any causal explanations of phase control would be appreciated.
Edit: Originally I thought it was a regular transistor and not a triac.
Best Answer
A triac (and snubber circuit, if present) will leak a certain amount of current, so it's not realistic to measure the output without a load.
The best way to test the output is with the motor connected as a load. If the voltage measured across the motor is not more than zero, measured on the AC VOLTS range of any multimeter, it's not going to turn. It's rare that a triac fails in the open state, normally they'll fail "on" and you'll get full RPM.