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!