09-09-2017, 11:06 AM
A voltage controller also called AC voltage controller or AC controller, is an electronic module based on thyristors, TRIACs, SCRs or IGBTs, which converts a fixed voltage, fixed frequency AC power source to obtain a voltage variable in the output delivered to a resistive load. This varied voltage output is used to dim street lights, vary heating temperatures in homes or industry, control the speed of fans and winders and many other applications, much like an auto-transformer. The voltage control modules are under the control of the power electronics. Because they are low maintenance and highly efficient, voltage controllers have largely replaced modules such as magnetic amplifiers and saturable reactors in industrial use.
A single-phase AC controller (voltage controller) is used to vary the value of the AC voltage after it has been applied to a load circuit. A thyristor is also placed between the load and the constant source of alternating voltage.
The average quadratic alternating voltage is regulated by changing the trigger angle of the thyristor. In the case of phase control, the thyristors are used as switches to establish a connection from the AC input power to the load circuit during each input cycle. For each positive input voltage, a cut is made and the voltage is reduced.
Circuit diagram with resistive load
During the middle of the cycle, the thyristor switch is turned ON to allow the voltage input to appear through the load. This is followed by the OFF state during the last half cycle to disconnect the load from the source voltage.
When the trigger angle α is controlled, the RMS value of the load voltage is also controlled. Therefore, the activation angle α is defined as the value of ωt at which the thyristor is activated.
A single-phase AC controller (voltage controller) is used to vary the value of the AC voltage after it has been applied to a load circuit. A thyristor is also placed between the load and the constant source of alternating voltage.
The average quadratic alternating voltage is regulated by changing the trigger angle of the thyristor. In the case of phase control, the thyristors are used as switches to establish a connection from the AC input power to the load circuit during each input cycle. For each positive input voltage, a cut is made and the voltage is reduced.
Circuit diagram with resistive load
During the middle of the cycle, the thyristor switch is turned ON to allow the voltage input to appear through the load. This is followed by the OFF state during the last half cycle to disconnect the load from the source voltage.
When the trigger angle α is controlled, the RMS value of the load voltage is also controlled. Therefore, the activation angle α is defined as the value of ωt at which the thyristor is activated.