C440B

Thyristors - SCRs are types of semiconductor switches that have three or four terminals and can control large currents when turned on. One type of thyristor is C440B which is a standard, four layer resistor with an active gate control. This application field of C440B is normally referred to as a "gate turn-off" (GTO) switch as it turns off when the gate current reverses, rather than staying on. It is most commonly used in applications such as adjustable speed drives, HVAC controls, and welding machines.

The C440B has two different operating modes: "on" and "off". When the gate voltage is zero, the thyristor is off and no current flows through the device. When the gate voltage is increased, the thyristor turns on and current flows from the anode to the cathode. This current will continue to flow until the gate voltage drops below a certain value, causing the thyristor to switch off. The process of turning the thyristor on and off by applying and removing a gate voltage is referred to as “gating”.

In addition, the C440B has two different types of operation: "control-OFF" and "control-ON". Control-OFF is when the gate voltage is high enough that it causes the switch to turn off. This is the most common operating mode used in HVAC and welding applications. Control-ON is when the gate voltage is low enough that it causes the switch to stay on. This operating mode is usually used in adjustable speed drives and other applications where the thyristor needs to stay on for long periods of time.

The working principle of the C440B thyristor is based on the three-layer diode structure, which has an anode, cathode and active gate, which allows for control of current flow. When the gate voltage is applied, the thyristor will turn on and current will flow from the anode to the cathode. When the gate voltage is removed, the thyristor will turn off and no current will flow. The amount of current that is allowed to flow through the thyristor is determined by the gate voltage, which also controls the “on/off” switching times.

In conclusion, C440B thyristors are a type of gate turn-off switch that can be used in a variety of applications, such as adjustable speed drives, HVAC controls, and welding machines. It has two operating modes - “control-OFF” and “control-ON” and works on the principle of three-layer diode structure, with an anode, cathode and active gate control. The current flow through the thyristor is determined by the gate voltage and it can be used to switch currents up to several hundred amperes.