Single Phase Inverter question

[Lancie1]

i tried already using some resistors..

Did you use resistors WITH the existing speed control (minus the speed control potentiometer), or simply resistors connected to the motor?

 

[leitmotif]

One would think that a variable freq and voltage power supply for single phase motors would be out there. This outfit has (or claim to) options for this

http://www.controlres.com/applications.php

ASSUMING this is a class project and your instructor has you tasked to build a variable speed control for single phase motor an off shelf unit does not complete your assignment.

I believe single phase motor speed control could be done but the real world is that most motor speed control historically has been DC and in this era (last 20 years or so) ends up to be three phase. Single phase is not done just because there is so little demand for it. The need for small (fractional HP) motor speed control is now satisfied with 3 phase motor and VFD designed for single phase power supply.

One bit of caution regarding your project. Install a switch that is 3 or four feet away from any connections. When doing testing trial runs you can use this switch to energize and deenergize safely. Do NOT rely on a wall plug to turn off or on they CAN emit enough flash to burn your hand.

Dan Bentler

 

[Gil47]

Here is a single phase variable frequency drive that you can connect to a PLC....

Minarik

If you read page 18 of the Minarik manual it shows that it is connected to a 3 phase motor, not a single phase motor.

eddycheong You commented that you tried it with resistors and it slowed down all you were doing was restricting the current flow to the motor by making heat

The unit that leitmotif shows in his post is a smarter version of the dimmer control you already have, that has the ability to be controled by an analog from a PLC.

Again I will say that a VFD will not run a single phase motor.

 

[AJZ]

Two products that claim to be able to control a single phase motor:
http://www.fanhandler.com/ and http://www.icmcontrols.com/products/category.php?cat_pk=19.
These products are designed to control furnace blower motors or airconditioning condensor motors.

 

[leitmotif]

If you read page 18 of the Minarik manual it shows that it is connected to a 3 phase motor, not a single phase motor.

eddycheong You commented that you tried it with resistors and it slowed down all you were doing was restricting the current flow to the motor by making heat

The unit that leitmotif shows in his post is a smarter version of the dimmer control you already have, that has the ability to be controled by an analog from a PLC.

Again I will say that a VFD will not run a single phase motor.

Eddy
Just to clarify
You CAN run a single phase motor off three phase either from two of 3 of the lines or a line and neutral.
In theory you could do this using a VFD designed for 3 phase
BUT
many VFDs are equipped to sense and trip if a 3 phase motor burns a winding out or one of the lines opens (single phases).
the VFD will sense the output current (current drawn by motor) and will trip if the phase currents are not the same which would be the case with a single phase motor tied across 2 of 3 legs of the VFD 3 phase output.

Dan Bentler

 

[eddycheong]

ya i've tried the resistors including the dimmer..i will look around if there is any VFD for my motor in my country

 

[DickDV]

I don't know, guys, I think you've all missed the main point here. Most single phase motors are designed to operate at a single frequency. They are, in effect, tuned devices. The second phase which has to be fabricated somehow inside the motor (usually with caps or caps and coils) are tuned to their design frequency, either 50 or 60Hz.

You can find variable frequency AC sources including inverters but the problem is in the motor. It simply doesn't want to run anywhere but at its design speed.

With the exception of a universal motor, single phase motors have to struggle like crazy simply to start from a full stop. Trying to do it with an off-design frequency may be the stuff lab experiments are made of, but, in the world where these machines have to do something useful, it just doesn't work.

I know there are obscure exceptions. But that's not what this is about.

 

[Gil47]

Thank you DickDV

A single Phase motor on a VFD will do many things, they will sing, they will hum, they will vibrate, they will smoke, they will boil water, or fry an egg.

But they bloody well will not cause the motor to turn and rotate.

 

[krk]

Hi,

Actually, there are now controllers available that will control the speed of a any single phase motor between 0 - 250% of the nameplate value, give you full torque over the whole range and have the facility for reversing the motor.

These controllers use the new 'CIGAM' technology to achieve this amazing feat.

I'll dig out the links and post them later.

 

[eddycheong]

will wait for your link

 

[Steve Bailey]

eddycheong,

I think you've already waited too long. CIGAM technology only works one day a year.

 

[Lancie1]

These controllers use the new 'CIGAM' technology to achieve this amazing feat.

I'll dig out the links and post them later.

April 1, 2008: April's Fool joke?

 

[hed]

perhaps this helps
http://www.educypedia.be/electronics/powermotor.htm

 

[eddycheong]

thx for all the replies..1 more thing how can i change the motor direction..my friend told me he manage to reverse the 3 ph motor by change the hot wire connection to the inverters, but that is 3 ph motor

 

[plcsoftvsd]

Hello Cntrlfrk,

Just opened the pdf file...What is the significance of L1 L2 L3?

is it 230 volts 3 phase drive?