Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

VFD to control 3 phase AC induction motor 400V 6000 rpm

Status
Not open for further replies.

dexterbot80

Member level 1
Joined
Oct 31, 2017
Messages
40
Helped
0
Reputation
0
Reaction score
0
Trophy points
6
Activity points
557
Hello,
I want to control the speed of a woodcutter that is equipped with an asynchronous three-phase motor 400V 6000 RPM 6KW.
From the searches I came to the conclusion that a VFD would successfully solve my problem so I decided to build one.
**broken link removed** seems to me the simplest solution for adjusting the frequency - I tested this circuit and obtained a three-phase sinusoidal signal.
This is the control circuit
CONTROLL BOARD.png

This is the gate driver circuit
GATE DRIVE.png

Please help me to better understand how the control circuit works and tell me if the electronic circuit is correct.
Basically, I have to get 6 Hi / Lo signals that will command the three-phase IGBT bridge.

Thank you
 

The motor can be connected both star and delta and works perfectly if it is fed to the grid.
bQse1.jpg
The problem is that the engine needs to reach a speed of 6000 rpm and I need a VFD to control the speed
 
Last edited:

Hello,
I want to control the speed of a woodcutter that is equipped with an asynchronous three-phase motor 400V 6000 RPM 6KW.
From the searches I came to the conclusion that a VFD would successfully solve my problem so I decided to build one.
**broken link removed** seems to me the simplest solution for adjusting the frequency - I tested this circuit and obtained a three-phase sinusoidal signal.
This is the control circuit
View attachment 151886

This is the gate driver circuit
View attachment 151887

Please help me to better understand how the control circuit works and tell me if the electronic circuit is correct.
Basically, I have to get 6 Hi / Lo signals that will command the three-phase IGBT bridge.

Thank you


This circuit creates the signals. But to drive a motor you need a power stage. 6 IGBTs and 6 gate drivers. Or you can just buy a compact IPM where all of them is inside. You can then attach this signal generator to your IPM.

google for intelligent power modules.
 

This circuit creates the signals. But to drive a motor you need a power stage. 6 IGBTs and 6 gate drivers. Or you can just buy a compact IPM where all of them is inside. You can then attach this signal generator to your IPM.

google for intelligent power modules.

My gate driver circuit is part of the power stage - i have 3x gate drivers for 3x IGBT half bridges
I have 3 IGBT modules for the motor driver https://www.semikron.com/dl/service-support/downloads/download/semikron-datasheet-skm50gb12t4-22892000/
 
Last edited:

I'm already stumbling upon the motor specification. What is it? 6000 rpm at 100 Hz? Industry standard motors are specified for either 50 or 60 Hz.
 
I'm already stumbling upon the motor specification. What is it? 6000 rpm at 100 Hz? Industry standard motors are specified for either 50 or 60 Hz.

Please excuse me - I misinterpreted. The engine is three-phase 400 rpm 3000 rpm and I would like to use this VFD to bring it at 6000 rpm.
 

Please help me to better understand how the control circuit works

Simulation showing basic operation of SPWM through H-bridge. Each op amp contains a half-bridge in the output stage. Filtering is through low-pass LC second-order type.

Fundamental frequency =100 Hz. The 1700 Hz carrier is slow so as to allow all waveforms to be easily seen in scope traces. (Your carrier is a much higher frequency.)
The load calculates as 80 ohms. 400VAC has peaks of 560V. To make it easy I gave it 1/3 of your 6 kW spec.

2 opamps 560VDC spwm 100Hz LC filter 400VAC sine to 80 ohm load.png

Each op amp is fed 100 Hz sine wave, at inverted polarity from the other.

My inductor L value is high due to the slow carrier frequency. You may choose a lesser L value. (The aim is so it passes your desired Ampere flow.) Select C so it provides power factor correction (in addition to supplementing a filtering role). C usually carries almost as much current as the load.

At reduced sine frequencies, it's possible the motor draws greater current (which is typical behavior). It may be necessary to experiment with L & C values, to find a suitable combination for your system.
 
My gate driver circuit is part of the power stage - i have 3x gate drivers for 3x IGBT half bridges
I have 3 IGBT modules for the motor driver https://www.semikron.com/dl/service-support/downloads/download/semikron-datasheet-skm50gb12t4-22892000/

Ok. It is possible to increase the frequency and get 6000 rpm (100Hz) for a 2 pole motor. But notice that if you increase the frequency of the motor over the specification (50Hz/60Hz) , the motor will degrade power. Very rough estimation at 6000rpm a 6kW power may decrease to 3kW. But it is not linear. After some certain frequency, it may be that there is a saturation and the motor just stalls.

I have a 3 phase asynchronous motor running @20.000 rpm (333Hz). 0.25kW. (But the case looks like a 0.75kW motor). I fed it through a standard mitsubishi inverter capable of delivering 1000Hz.

You have a chance up to 6000rpm with a standart motor, but with remarkable power degradation.

After 10.000rpm the power decreases too much or the motor even stalls and you need to change the design of the motor (coils, stator etc.)
 

Hi,

If you adjust frequency you need to adjust voltage, too.

This means at 100Hz you need about doubled voltage.

With async motors this is not that criticle as with synchronous motors or BLDC motors.

Klaus
 
Simulation showing basic operation of SPWM through H-bridge. Each op amp contains a half-bridge in the output stage. Filtering is through low-pass LC second-order type.

Fundamental frequency =100 Hz. The 1700 Hz carrier is slow so as to allow all waveforms to be easily seen in scope traces. (Your carrier is a much higher frequency.)
The load calculates as 80 ohms. 400VAC has peaks of 560V. To make it easy I gave it 1/3 of your 6 kW spec.

View attachment 151912

Each op amp is fed 100 Hz sine wave, at inverted polarity from the other.

My inductor L value is high due to the slow carrier frequency. You may choose a lesser L value. (The aim is so it passes your desired Ampere flow.) Select C so it provides power factor correction (in addition to supplementing a filtering role). C usually carries almost as much current as the load.

At reduced sine frequencies, it's possible the motor draws greater current (which is typical behavior). It may be necessary to experiment with L & C values, to find a suitable combination for your system.

Hello, From what I see here you propose another bridge control scheme. Can you help me to implement your idea in my circuit? It would be much easier for me. Thank you
 

Hi,

If you adjust frequency you need to adjust voltage, too.

This means at 100Hz you need about doubled voltage.

With async motors this is not that criticle as with synchronous motors or BLDC motors.

Klaus

Hello, I have an asynchronous motor 400V 3000rpm that I want to bring it 6000rpm. I am interested in the behavior of the engine at the maximum speed of 6000 rpm and what possibilities exist to make a VFD as efficient as possible.
 

Ok. It is possible to increase the frequency and get 6000 rpm (100Hz) for a 2 pole motor. But notice that if you increase the frequency of the motor over the specification (50Hz/60Hz) , the motor will degrade power. Very rough estimation at 6000rpm a 6kW power may decrease to 3kW. But it is not linear. After some certain frequency, it may be that there is a saturation and the motor just stalls.

I have a 3 phase asynchronous motor running @20.000 rpm (333Hz). 0.25kW. (But the case looks like a 0.75kW motor). I fed it through a standard mitsubishi inverter capable of delivering 1000Hz.

You have a chance up to 6000rpm with a standart motor, but with remarkable power degradation.

After 10.000rpm the power decreases too much or the motor even stalls and you need to change the design of the motor (coils, stator etc.)

I understand it will drastically decrease the power to about 100Hz. How do we make this VFD as effective as possible? Would it be a solution to change the 6KW motor with an 11KW motor to get the 6KW at the top speed of 6000rpm?
 

The available torque of an asynchronous motor will reduce roughly with the square of applied voltage. Running a motor with double frequency and same voltage gives about 1/4 of the nominal torque and thus 1/2 the mechanical power.

Related to post #3, you didn't tell if 400V operation uses star or delta connection.
 

The available torque of an asynchronous motor will reduce roughly with the square of applied voltage. Running a motor with double frequency and same voltage gives about 1/4 of the nominal torque and thus 1/2 the mechanical power.

Related to post #3, you didn't tell if 400V operation uses star or delta connection.

The motor can be connected to both star and delta. I will use the version recommended by you professionals. I need this VFD for optimum woodworking. I hope to manage to build it as quickly as possible.
 

Obviously it can be connected star or delta. The question is, which configuration is used for 400V, full power, in other words, is it a 230/400V or a 400/690V motor?

- - - Updated - - -

I'm sure that it's cheaper to buy a Chinese VFD than to start developing your own. The post #1 control circuit makes no sense for me, by the way.
 

Obviously it can be connected star or delta. The question is, which configuration is used for 400V, full power, in other words, is it a 230/400V or a 400/690V motor?

- - - Updated - - -

I'm sure that it's cheaper to buy a Chinese VFD than to start developing your own. The post #1 control circuit makes no sense for me, by the way.

I think the motor is 400 / 690V - it does not work at 230V. As for cheap VFD made in china I do not even think. I have had the opportunity to use this and have succumbed very quickly. We have called on you professionals to solve this problem - I accept any modification of the command circuit just to work and to be as simple as possible - the idea of ​​arduino 3 phase DDS seems very good and very affordable.
 

I understand it will drastically decrease the power to about 100Hz. How do we make this VFD as effective as possible? Would it be a solution to change the 6KW motor with an 11KW motor to get the 6KW at the top speed of 6000rpm?

Using a 11kW motor @6000 rpm is maybe not the most effective solution but it is a solution. If the motor has a belt pulley, you can try to change the speed mechanically. (by adjusting the diameter of the pulley).

Frequency inverters are really cheap. They cost for 7.5kW-11kW between 150-350 USD in aliexpress.com. Most can drive up to 400Hz.

https://www.alibaba.com/product-detail/High-performance-AC-drive-three-phase_60734357792.html?spm=a2700.7724838.2017115.44.77da4d33E3o2ah&s=p
 

Using a 11kW motor @6000 rpm is maybe not the most effective solution but it is a solution. If the motor has a belt pulley, you can try to change the speed mechanically. (by adjusting the diameter of the pulley).

Frequency inverters are really cheap. They cost for 7.5kW-11kW between 150-350 USD in aliexpress.com. Most can drive up to 400Hz.

https://www.alibaba.com/product-detail/High-performance-AC-drive-three-phase_60734357792.html?spm=a2700.7724838.2017115.44.77da4d33E3o2ah&s=p

If we buy everything as we develop ourselves? How about the passion for electronics? I think it's far more beneficial if I solve this problem here - I think many of our children will have a lot to learn. So the benefit would be millions of times bigger than if I bought a VFD.
 

Your motor's windings dictate whether you shall wire the power supplies as a delta or as a wye. Create the full 3-phase simulation to see if any short circuits occur.

Hello, I built the command circuit and tested with the IR2113 driver and a tri-phase bridge of 6 igbt. Each halfbridge goes into a short circuit immediately after I start the circuit( without the engine being connected to the output) . I think there is no dead time between Hi and Lo signals and my Hi and Lo IGBTs starts in the same time. Please help with this.
Thank you
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top