AC Motor Speed Controller Circuit

Thread Starter

Fanfire174

Joined Mar 13, 2018
209
Hi guys,

I am trying to design a circuit for controlling the speed of motor

It should be do following

1. Need to control speed of motor

2. Can be turn on/ off by microcontroller


Product Specification:-

· Warranty : 1 year
· Voltage : 415 Volt
· Horsepower : 0.25 HP
· Speed : 1440 RPM
· Brand Name : MGM
· Number Of Items : 1
· Product Type : Flange type
· Phase : 3 PhAse
· Power : 0.18 Kwatt


Product information
https://www.indiamart.com/proddetail/mgm-0-25-hp-flange-type-ac-motor-sm63-b4-10978226830.html


I found the following circuit to control the speed of motor on the internet

upload_2019-2-18_14-42-59.png

It would be very helpful if someone could help me with suggestions and/or circuits.
 

LesJones

Joined Jan 8, 2017
2,317
You need to use a VFD (Variable frequency drive.) to the control the speed of a three phase induction such as the one you have. As the motor is shown as requiring 415 volts phase to phase you will need a VFD capable supplying this voltage. These are more expensive than those that supply that supply 240 volts phase to phase. Your motor will probably be configured in star configuration. It MAY be possible to configure it to delta configuration which would allow it to run on 240 volts phase to phase. The speed controller you show is only suitable for a series wound (Universal.) motor.

Les.
 

Thread Starter

Fanfire174

Joined Mar 13, 2018
209
You need to use a VFD (Variable frequency drive.) to the control the speed of a three phase induction such as the one you have. As the motor is shown as requiring 415 volts phase to phase you will need a VFD capable supplying this voltage. These are more expensive than those that supply that supply 240 volts phase to phase. Your motor will probably be configured in star configuration. It MAY be possible to configure it to delta configuration which would allow it to run on 240 volts phase to phase. The speed controller you show is only suitable for a series wound (Universal.) motor.

Les.
Thanks for valuable suggestion

I googled for variable frequency drive circuit http://electronics-diy.com/1000w-ac-motor-speed-controller.php



What are the component required if I want to design my own VFD circuit ?
 
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LesJones

Joined Jan 8, 2017
2,317
It is much cheaper to buy a ready made VFD than it would be to build one. If you have to ask what the components on the block diagram do then you will have an awful lot to learn before you will be capable of designing one.

Les.
 

Thread Starter

Fanfire174

Joined Mar 13, 2018
209
It is much cheaper to buy a ready made VFD than it would be to build one. If you have to ask what the components on the block diagram do then you will have an awful lot to learn before you will be capable of designing one.

Les.
but as seen on internet there are only few components need to make

as shown in circuit



I don't need immediately I want to learn by doing experiment
 

LesJones

Joined Jan 8, 2017
2,317
That is nothing like a VFD. It is only a switching circuit that switches on at a variable position in the waveform. I you think of each 180 degrees of the sine wave then if the switch (SCR or Triac.) switches on at close to zero degrees the load receives the full amount of power. If it does not switch on until the 90 degree point (Crest of the waveform.) then the load would only have power applied to it for half of the time so the average power would be half. A VFD synthesises a three phase waveform with a variable frequency. As the frequency is varied it also has adjust the amplitude of the waveform as the reactance of the motor windings changes with frequency. This is a link to one of many descriptions of how a VFD works to be found on the internet.

Les.
 

Thread Starter

Fanfire174

Joined Mar 13, 2018
209
That is nothing like a VFD. It is only a switching circuit that switches on at a variable position in the waveform. I you think of each 180 degrees of the sine wave then if the switch (SCR or Triac.) switches on at close to zero degrees the load receives the full amount of power. If it does not switch on until the 90 degree point (Crest of the waveform.) then the load would only have power applied to it for half of the time so the average power would be half. A VFD synthesises a three phase waveform with a variable frequency. As the frequency is varied it also has adjust the amplitude of the waveform as the reactance of the motor windings changes with frequency. This is a link to one of many descriptions of how a VFD works to be found on the internet.

Les.
Hi Les

Thank's for link and description. can you suggest how to design my own VFD?

I can use a single phase motor for the experienment. I have seen some material on the internet and still reading some links

Basic VFD :

Part 1 : rectifier (where AC is converted to DC);

Part 2 :the DC intermediate circuit for filtering.

Part3 : DC-to-AC inverter where DC is turned back to three-phase AC
 
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LesJones

Joined Jan 8, 2017
2,317
Single phase induction motors do not work well running from a supply at a different frequency to their design frequency.

Les.
 

Thread Starter

Fanfire174

Joined Mar 13, 2018
209
Single phase induction motors do not work well running from a supply at a different frequency to their design frequency.

Les.
okay alright but still my question is same How to build my own VFD ?

as found on the internet I need following

Basic step to make VFD :

Part 1 : rectifier (where AC is converted to DC);

Part 2 :the DC intermediate circuit for filtering.

Part3 : DC-to-AC inverter where DC is turned back to three-phase AC

Where to start for the circuit ?
 

Reloadron

Joined Jan 15, 2015
4,508
Designing and building a 3 Phase VFD (Variable Frequency Drive) from discrete components is not an easy task. One method is to start with a single phase AC input and convert that to DC. The DC is then used to drive a 3 phase AC inverter capable of variable frequency. Your components need to be rated for the voltage and current demand of your motor.

Your motor looks to be a small fractional horsepower motor (1/4 HP) but even at the low HP the inverter design is not a simple task. You are better to buy than build. You may also want to just consider using a simple DC motor with a speed control for single phase operation. Simply because 1/4 HP is a small motor.

You may want to give this a read, Connecting Variable Frequency Drive (VFD) to a 3 Phase Motor, to understand better what is going on. Three phase VFDs for smaller fractional HP motors have become relatively inexpensive.

Ron
 

Thread Starter

Fanfire174

Joined Mar 13, 2018
209
Designing and building a 3 Phase VFD (Variable Frequency Drive) from discrete components is not an easy task.
i am a little bit disappointed by your statement. I wanted to try my best attempt to solve problem

One method is to start with a single phase AC input and convert that to DC. The DC is then used to drive a 3 phase AC inverter capable of variable frequency. Your components need to be rated for the voltage and current demand of your motor.
It's good to start and I have to invest my time to know more about VFD
 

Reloadron

Joined Jan 15, 2015
4,508
i am a little bit disappointed by your statement. I wanted to try my best attempt to solve problem


It's good to start and I have to invest my time to know more about VFD
I am not saying trying to design an inverter is a bad idea. But let's consider something. The guys who design these inverters generally have their BSEE and additional years designing such products. Designing down to the component level and then designing down to the circuit board level takes years of experience in the specific field. It's not as simple as buying a box of parts and making a 3 phase VFD inverter just happen. Even with a schematic and parts list in hand you need to design a circuit board (or two) where component layout is critical. My statement was not intended to disappoint but rather have you understand what is involved.

Your first posted image was a single phase shift SCR circuit. Everything we see on the Internet is not gospel. Since you posted this in the Embedded Systems and Micro Controller Section I assume you plan control using a micro-controller? Should that be true then you may want to consider a BLDC (Brush Less Direct Current) type motor. These can be driven using a uC much easier than building a 3 phase VFD. The point here is there is quite a lerning curve before designing a 3 phase VFD drive.

Ron
 

Thread Starter

Fanfire174

Joined Mar 13, 2018
209
I am not saying trying to design an inverter is a bad idea. But let's consider something. The guys who design these inverters generally have their BSEE and additional years designing such products. Designing down to the component level and then designing down to the circuit board level takes years of experience in the specific fieldRon
Hello Ron
I agree with you I know to build any circuit we should have experience but experience come by doing an experiment
.
Since you posted this in the Embedded Systems and Micro Controller Section I assume you plan control using a micro-controller?
Ron
I posted a question in Embedded Systems and Micro Controller Section because I want to turn on/off by microcontroller. I can do with relay and opt-coupler

I am not an expert but trying to learn as I can do, I have knowledge of microcontroller but I don't have knowledge in power electronics.

we can't good in many fields so I thought I should ask a question here

Here are more experienced people so I thought someone could help me to build the circuit
 

Thread Starter

Fanfire174

Joined Mar 13, 2018
209
as given link by Les

I understand the rectifier and filter circuit but I don't have knowledge about inverter circuit. I can make a circuit diagram as well as layout diagram

 

Reloadron

Joined Jan 15, 2015
4,508
With that in mind I would start with a simple Google of "BLDC Motor Control Arduino" which will afford you some simple designs. There are dozens of micro-controller circuits available out there and since Arduino is pretty common you will find a wide range of motor speed control circuits and more important you will get a basic understanding of how they work. You will become familiar with the software code and why it does what it does. This will also allow getting started on a small and less expensive path. That would be my suggestion.

<EDIT> Just saw your last circuit. Now the trick becomes understanding what the transistors do and why. </EDIT>

Ron
 

Thread Starter

Fanfire174

Joined Mar 13, 2018
209
as said by Ron and we also know that everything on the internet is not true

I have some option like max has given link and keepitsimplestupid has given link

Now I need an someone who can probably ensure me that it might be work so that I can purchase required parts for following motor specification

Product Specification:-

· Voltage : 415 Volt
· Horsepower : 0.25 HP
· Speed : 1440 RPM
· Brand Name : MGM
· Number Of Items : 1
· Product Type : Flange type
· Phase : 3 PhAse
· Power : 0.18 Kwatt

, Someone has done work practically to similar project before
 
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