Figure 1 shows the symbol of a quadrac.
They use the same body as power transistors.
Specifications
The specifications of a quadrac are the same as a triac and a diac. The maximum MT1 voltage, maximum current, and trigger point are indicated by the manufacturer.
A part number or type number is used to design the component.
Where they are found
Quadracs are not common today. They can be found in old motor controls, Iamp dimmers, and some electric appliances where the speed of a motor, temperature, or any amount of power applied to an AC Ioad must be controIIed.
The basic application is the same as a triac in power controls as explained in the article that explains how the triac works.
Testing
The multimeter can only reveal if the quadrac is shorted. Low resistance between any of the three terminals indicates a problem.
