IGBT and its Usage in Motor Control

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The IGBT, Insulated Gate Bipolar Transistor, is a switching transistor that is driven by voltage applied to the gate terminal. Device structure and operation are identical to those of an Insulated Gate Field Effect Transistor, generally known as a MOSFET. The primary dissimilarity between the two device types is that the IGBT uses conductivity modulation to reduce on-state conduction losses which MOSFET does not do.

IGBT is a device that integrates the voltage feature of a bipolar transistor (collector – emitter) and the drive feature of a MOSFET. The key reason behind the flourishing popularity of IGBT is its superiority at high speed switching applications. This device is well-known for integrating high efficiency and fast switching. It is mainly used as an electronic switch in many modern appliances: variable-frequency drives (VFDs), electric cars, trains, variable speed refrigerators, air-conditioners and even stereo systems with switching amplifiers. Today we will discuss about usage of IGBT in motor control.

Advancements of highly capable motor drives are very essential for industrial applications. Satisfactory dynamic speed command tracking and load regulating response are two must needs, for a high performance motor drive system. DC motors excel in terms of speed control for acceleration and deceleration. The power supply of a DC motor joins right away to the field of the motor which approves for accurate voltage control, and is required for pace and torque control applications. Because of their simpleness, ease of application, dependability and auspicious cost, DC drives have long been a mainstay of industrial applications. Because of low horsepower ratings, DC drives are usually less costly in comparison with AC drive systems. DC motors are being used as adjustable speed machines traditionally and an extensive extent of options has developed for this intention.

To obtain sufficient levels of power handling capability, especially in motor control applications those demand multiple drive elements, power integrated circuits have been developed using hybrid constructions of the distinct transistors. Hybrid techniques have been necessary and useful due to the power handling limitations of monolithic power integrated circuit technology. Power integrated circuit design has often been limited by the absence of power packages that provide the low thermal impedance and high performance switching necessary for reliable operation. The switching elements of these modules, which may be Insulated Gate Bipolar Transistors (IGBTs) or various forms of thyristors, “chop” low-frequency (e.g., 60 Hz or dc) voltages /currents at the input / output port into high-frequency square wave pulses of variable width (20 to 200 ms).

The silicon GTO was the only available power semiconductor switching device until the 1990s. It had power conducting ability compatible for motor control applications. The ratings of IGBTs had adequately developed in the 1990s. It overcame one Megawatt which allowed entrance of the IGBT into the traction market. The availableness of the IGBT made allowance for notable advancements in the motor drive technology due to exclusion of snubber circuits and an raise in the operating frequency of the inverter circuit employed to transfer power to the motors.