A gate turn-off thyristor (GTO) is a type of thyristor that can be turned off by means of a voltage applied between its gate and cathode terminals.
Some key things to know about GTO thyristors:
- Construction: They consist of four alternating layers of P-type and N-type semiconductor material, with three terminals – anode, cathode and gate.
- Operation: Like a standard thyristor, a GTO thyristor latches on when gate current triggers it. But applying a negative voltage between gate and cathode turns it off by cutting off the supply of charge carriers.
- Switching: GTOs allow very fast switching compared to other thyristors. Switching times can be as low as hundreds of nanoseconds.
- Applications: Used in inverters, motor controls, ignition circuits, battery chargers etc. where fast and reversible power flow is needed.
- Power ratings: Can switch large currents up to thousands of amps and withstand voltages up to 5 kV or more. Offer high power handling capability.
- Advantages: Fast and reversible power control. Can be turned on and off like conventional power transistors.
- Drawbacks: Require complex drive circuitry. Have lower conductivity when on compared to standard thyristors. Prone to damage if turned on at wrong times.
GTO thyristors integrate the power handling of standard thyristors with the switching capability of transistors, making them suitable for high power applications requiring fast and reversible current control.
What are some common applications where GTO thyristors are used?
- Variable frequency drives (VFDs) – Used to control the speed of 3-phase AC motors by varying the frequency of power supplied. Important use in industrial equipment.
- UPS systems (uninterruptible power supplies) – GTOs allow fast switching between utility power and backup battery power sources to provide stable output.
- Welding equipment – Arc welders, plasma cutters, furnaces use GTOs for precise control of high welding currents.
- High voltage DC power transmission – GTOs enable efficient conversion between AC and DC, allowing power transmission over long distances with low losses.
- Traction motor control – Powering electric locomotives, subways, mining vehicles by controlling traction motors using GTOs.
- Static VAR compensators – Provides fast reactive power compensation on transmission grids to regulate voltage using GTO thyristor switches.
- Battery chargers – GTOs enable fast, reversible switching to efficiently charge battery banks like in electric vehicles.
- Fluid heating – Resistive fluid heaters for process industries rely on GTOs to precisely modulate large currents for temperature control.
- Magnetic equipment – GTOs regulate high inrush currents for applications like inductive melting furnaces, magnetic separation devices.