Power Electronics Devices and Circuits

What is an SCR (Silicon Controlled Rectifier)?

• A 4-layer, 3-terminal device (Anode, Cathode, Gate) that works as a controlled rectifier, conducting when a gate pulse is applied and remaining on until the current falls below the holding current. Used in rectifiers, inverters, and motor control.

• A simple diode that allows current to flow in one direction only.

• A type of transistor that can amplify signals but cannot control current flow.

• A capacitor used for energy storage in power circuits.

What is a Chopper (DC-DC Converter)?

• It converts fixed AC input to variable AC output.

• It converts fixed DC input to variable DC output, with types including Step-down (buck), Step-up (boost), and Buck-boost.

• It is used primarily for converting AC to DC power.

• It is a device that regulates voltage in an AC circuit.

What is a TRIAC (Triode for AC)?

• A 3-terminal device that can conduct current in both directions, commonly used in lamp dimmers, fan regulators, and AC power control.

• A type of diode that only conducts in one direction, used in low-power applications.

• A 2-terminal device used for switching DC circuits.

• A high-frequency transistor used in radio frequency applications.

What is a Cycloconverter?

• A device that converts fixed AC at one frequency to variable AC at a lower frequency directly.

• A type of transformer that steps up voltage levels.

• A rectifier that converts AC to DC for battery charging.

• An inverter that converts DC back to AC for grid connection.

What is the function of a UJT Triggering Circuit?

• A Uni-Junction Transistor generates sharp triggering pulses, with a UJT relaxation oscillator charging and discharging a capacitor to provide periodic gate pulses for SCR, ensuring reliable firing control.

• A UJT Triggering Circuit amplifies weak signals to drive high-power devices.

• A UJT Triggering Circuit is used to convert AC signals into DC signals for better efficiency.

• A UJT Triggering Circuit regulates voltage levels in power supply systems.

What is a Single Phase Bridge Inverter?

• A device that converts AC to DC using diodes.

• A circuit that converts DC to AC using four switches (SCRs, MOSFETs, or IGBTs), with output that can be square wave, quasi-square, or PWM-controlled AC, used in UPS, induction heating, and AC drives.

• A type of transformer that steps up voltage for transmission.

• A system that stores energy in batteries for later use.

What is a Phase Controlled Rectifier?

• A device that converts AC to DC using controlled switching devices like SCRs, with output DC voltage depending on the firing angle (α).

• A type of transformer that steps down voltage for AC circuits.

• A device that only allows current to flow in one direction without any control.

• A circuit that amplifies AC signals for audio applications.