Variable Frequency Drives Explained | VFD Basics - Part 2

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⌚Timestamps
00:00 - Intro
01:00 - VFD diagram
01:54 - How does an IGBT work?
03:58 - IGBT module in VFD

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Welcome to Part 2 of Variable Frequency Drives Explained!

As we have learned in the previous lesson, there are many applications where in order to meet varying demands, motors need to throttle down output.

Additionally, constantly running a motor at its full speed can be costly.

A variable frequency drive is a type of controller that has the function of driving an electric motor by varying the frequency and voltage that is supplied to control its speed and power.

VFDs are widely used in both industrial and commercial applications, such as control of fans, pumps, compressors, HVACs, and even roller coasters!

It is impossible to talk about VFDs and Insulated Gate Bipolar Transistors, also known as IGBTs without understanding what Pulse Width Modulation (PWM) is.

An analog input signal can be modulated by generating variable width pulses to represent its amplitude. In a very brief summary, PWM is a way to control analog signals with a digital output.

To understand the IGBT’s function in a VFD, it is important to understand how an IGBT works singularly.

At the simplest level, an insulated gate bipolar transistor (IGBT) is a switch used to allow power to flow when it is turned on and to stop when it is turned off.

It is important to note, however, that they have the capability of switching on and off several thousand times every second!

An IGBT is a solid-state device, which means it has no moving parts.

Rather than opening and closing a physical connection, it is operated by applying a voltage to a semiconductor component, called a gate, that changes its properties to create or block an electrical path.

IGBT terminals (pins) represent the Gate, the Collector, and the Emitter.
Current flows along the conductance path composed by the Collector and the Emitter, while the Gate controls the device.

Now that we have an understanding of how our IGBTs work, let’s go back to the application of IGBTs in VFDs, and let’s represent our IGBTs as contact switches for a simpler understanding.

The top IGBTs are in the positive DC bus, and the lowers are in the negative DC bus, so when one of the top switches is closed, that motor phase and voltage then become positive.

On the other hand, when one of the lower switches is closed, that motor phase and voltage then become negative.

Therefore, by controlling the speed and sequence that those switches open and close, we can control the phases and frequency of our signal: zero, negative, or positive.

It is important to note that VFDs output signal is a PWM signal, which turns out to be a rectangular waveform.

This wave is crucial in the operation of a VFD, as it is this variable voltage and frequency that will enable the VFD to control the motor’s speed.

VFDs output signal is a PWM signal, which turns out to be a rectangular waveform. This wave is crucial in the operation of a VFD.

The control processor of a VFD contains a program that is not typically user-accessible, however, there are many parameters and settings that can be adjusted and tuned for optimal VFD operation for each application where it’s been used to meet specific motor and driven equipment specifications and needs.

The following are common adjustable parameters and settings in a VFD:
- Tunable: Proportional, Integral, Derivative (PID)
- Minimum and Maximum Speed
- Current Limit

The number of parameters varies based on the level of complexity of the VFD. They can range from 50 to over 200 parameters!
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[mujeebahmadkhan]

The quality of these videos is beyond belief. So much helpful. Thanks @RealPars

[oficinadoeletricista]

Their videos are excellent lessons with a wealth of amazing information, a lot of detail and quality standard to admire.
I'm very grateful to the entire RealPars team for this excepcional content.
Congrats on mastery on the subject.
👏👏👏👏👏

[nambotheny]

It would be great for beginners like me by showing the parameters you used when designing the circuit

[zainaabdin]

I pity myself that such knowledge and development wasn't available on days when I was still productive and immersed in working

[jalil]

Thanks from your nice teaching we hope to share more videos with us

[vky]

very very very well indepth explaination, 👏 with easy understanding 👍

[silvestreortiz]

It would be really helpful if you can show how to install control wires!

[Militovec]

I recently changed my job and this is very helpful for my adaptation in the company. Thank you a lot

[ryanreed]

Part 1 was great! I have been waiting for this

[ahsan]

Sir your explanation is so Amazing thank you for your service 😊

[aircates]

I liked it better when I thought it worked on the principles of magic…. Now it makes sense….. Good explanation!

[roytutorialchannel]

Thank you very much for Teaching this video, I work Electrician

[pavunumuthu]

All video very super VFD topic amazing i am also Realpars big closely fan, from indian country state in Tamilnadu chennai.

[AlexandreSantos-ggil]

I watch all the videos of RealPars I'm a fan, from Brazil hugs.

[hakuzu]

Transistor has the same fonction than a contactor it just allowd the tension in 1 direction, the gate is the coil "a1 a2", the emettor and collector is "13 and 14" in the normaly open contact :)) that all

[joaofabri]

It was pretty good!! Just some VFD's don't have TC in Input

[nimbo]

Hi There,
For applications where bypass VFDs required, i come across with requirements of soft motor starters in the bypass line if the vfd fails. This is understandle as in the mode of failed vfs, the inrush current in the bypass line has to be softeneded before entering motor and since there is no soft starters by default, that would be the requirement.
What are the key differences between Manual bypass and E-bypass VFDs? For both VFD types, do soft starters need to be installed within the vfd housing?

[Flankymanga]

I would also like to suggest a topic: What is the purpose of pre-charge circuit and how does it work? Thank you!

[iacovacheiuliangheorghe]

Hello. I have a Romanian SP81sw bench lathe, it's small with an 80mm universal and it has a 0.37 kw / 380v motor. I only have a 220v network. What power should the VDF have for this motor, should I switch it to a VFD to run on 220v .Thank you!

[nguyenphucnguyen]

I understand that the PWM duty can be changed by some kind of processor, but about the frequency, how could we change the frequency to control motor speed?