Exchanging it up - IGBTs

An Insulated Gate BipolarTransistor (IGBT) is a key part of what makes up a VFD (Variable Frequency Drive). In the event that you separate a VFD, one simple approach to break down it is to consider it in three principle parts: the scaffold converter, DC join, and what we will discuss today, the inverter. An IGBT is the inverter component in a VFD, beating voltage quicker than we can even squint.

IGBTs have made some amazing progress since they were initially created in the 1980's. The IGBTs of today are considerably more progressed than their antecedents, which were moderate at exchanging current on and off and frequently had issues overheating when passing a high present. With each new era, IGBTs have kept on making strides. No more tormented by moderate rates, IGBTs have turned out to be exceptionally solid gadgets that can deal with high voltage gadgets and can switch in under a nanosecond (that is a billionth of a second)!

IGBTs are the "Watchmen" of Current

To comprehend an IGBT's part in a VFD, it is imperative to recognize how an IGBT takes a shot at a littler scale. As characterized by being a transistor, an IGBT is a semiconductor with three terminals which function as a switch for moving electrical current. Generally as "entryway" proposes, when the voltage is connected to the door, it opens or "turns on" and makes a way for current to stream between the layers. On the off chance that no voltage is connected to the door, or if the voltage is not sufficiently high, the entryway stays shut and there will be no stream of power. Along these lines, an IGBT acts like a switch; on when the entryway is open and streaming present and off when it is shut.

In this way, the IGBT acts as the switch used to create Pulse-Width Modulation (PWM). An IGBT will switch the current on and off so rapidly that less voltage will be channeled to the motor, helping to create the PWM wave. For example, although the input voltage may, in reality, be 650V, the motor perceives it as more like 480V by using PWM (shown in diagrams below). This PWM wave is key to a VFDs operation because it is the variable voltage and frequency created by the PWM wave that will allow a VFD to control the speed of the motor. Therefore, without the IGBT switching the current on and off so rapidly a PWM wave—and the speed control that comes with it— could not be created.

The number of pulses per second from the IGBTs is known as a carrier frequency. Since carrier frequency is an adjustable parameter on most VFDs, you can essentially set it as high or as low as you want. Although, adjusting the carrier frequency comes with a few tradeoffs. Setting the carrier frequency too high will reduce the acoustic noise level produced from the VFD, but it will also shorten the expected VFD life due to heat. A higher carrier frequency will also contribute to an increase in motor heating and affect the overall efficiency of the motor. On the other hand, if you are in a sound sensitive environment – or if you just don’t want a headache – setting the carrier frequency too low can create a lot of motor noise or whining from the VFD. We have found that setting your carrier frequency at about 2 Kilohertz will achieve a nice balance between the audible acoustics while still keeping your VFD running efficiently.

In a typical six pulse drive, there is six IGBTs pulsing voltage up to 15,000 times per second. Since their introduction in the 1980’s, IGBTs have literally switched up the market and now play a large role in many modern day power electronics applications where speed and process control are needed. It is clear that IGBTs play a large role in many power electronic applications and will continue to as they become more and more advanced in their technology. Hopefully taking this in-depth look at the small part an IGBT plays has helped you to understand the overall functionality of a VFD as well. Check out our other featured articles for everything you need to know about VFDs and motors at www.vfds.com/blog, or click on the banner below to find the VFD you are looking for out of our 2,000+ inventory!