reverse an AC motor

[njlee]

Hi all,

Are there ways to reverse a regular single phase fractional hp AC motor? I think switching the wires will not do it. Can I do it by using additional hardware (switches or controller or ...)??? Or Do I have to get special kind of motor.

Thanks,
Lee

 

[pablo02]

What is your application and how critical is it?

I once faced a similar situation when I was a kid (sold a special furnace motor -- had to order it) motor turned the wrong way: it was made where I could not pull the motor rotor out (swap end-bells), turn it end-for-end and stick it back in -- so, I pulled the winding out, flipped it and stuck it back in -- my boss bet me it wouldn't work -- I got the steak dinner...

so, I just gave you two ways possible ways to reverse your motor... of course, it will depend upon how your motor is built -- and you should be careful not to damage any wires or windings;

you may also be able to swap wire connections inside, but you'll need to know what wire goes where and this is probably beyond your scope based upon your question -- and it depends upon how it is made...

 

[GusD]

Hello njlee

You have to be able to switch the wires to be able to reverse rotation.The devices you mention will only provide
the means to reverse those same wires.The starting winding and running winding have to be made independent of each other.If there is a common connection, it will have to be open to allow reversing.I personally don't know of any other way to acomplish this.Pablo's idea is also another way of reversing the motor,even if somewhat impractical.If your reversing is a one time deal,go ahead and switch bracket ends like Pablo did.

GusD

 

[jbartos]

Suggestion to original posting: The motor direction of rotation should not be done without carefully checking the following:
1. Is the motor designed for one direction of rotation or for both.
2. Is there an arrow shown anywhere indicating direction of rotation.
3. Tech support of the motor manufacturer.

 

[njlee]

Hi All,

thanks for the reply!

I am using the AC motor to move a rotating device, so I need an easy way to reverse the motor repeatly (every 2-5 mins). Is AC motor ready out of the question for this kind of application?

I heard someone mentioned there is a way to temporarily convert the power source to DC power and hence be able to run the motor in reverse. is it even possible?

thanks again.

Lee

 

[jbartos]

Suggestion: Visit

http://www.sea.siemens.com/contrlbu/upld/files/p41-46.pdf

etc. for more info
DC voltage or power is applied to AC motors for braking purposes only.

 

[pablo02]

I suspect that the way the fractional hp motor is made, you will not be able to make it rotate one-way and then the other... maybe someone else can provide more details for what you need to do..

 

[SteveKW]

Njlee, can you go into detail on the motor you have? What color/numbers on wires, nameplate info, etc..

 

[Marke]

njlee

There are a number of diferent types of single phase fractional HP motors. Generally, there are three types, the universla motor (has brushes) the standard induction motor and what is often termed the reluctance motor.
If the motor has two windings, as in the case of the universl motor and the standard induction motor, you reverse the connection of one winding only. If the motor has only one winding, then you can not reverse it. Access to the two windings will usually require you to partially dismantle the motor and should only be done if you are familiar with this operation. As you are asking this question, I assume that you are not familiar, so you may need to seek the assistance of someone with the appropriate skills.

Best regards,

Mark Empson

http://www.lmphotonics.com

 

[janderson2]

Brush AC motors are designed to operate in one direction. The commutator is shifted for optimum performance.

If it is brushless and electronically commutated, then reversing is accomplished through the drive circuit.

 

[ScottyUK]

If you are reversing the motor every 2 -5 minutes, you may run into overheating problems, especially if the motor has a long acceleration time compared with the time it runs at full speed (e.g. 10s out of 2 mins, etc.). Also watch for overloading the contactor if the motor is not at standstill prior to reversing. If this is the case you will have to oversize the contactor or find one that is suitable for plugging duty (AC5 or AC6 I think, anyone who knows for sure please correct me). For a small motor, it will be easier to oversize it.

 

[jraef]

Another way to solve this is to replace your motor with a 3 phase version. 3 phase motors are easilly reversible. You can get inexpensive VFDs (Variable Frequency Drives) that will do the two things that you need: convert your 1 phase power to 3 phase and electronically reverse the motor. The VFD is probably the same installed cost as a switch to reverse a 1 phase motor. The only additional expense would be finding a suitable 3 phase motor. Here are some examples of both;

http://www.bodine-electric.com/Asp/...eries AC Induction Motor&Model=0274&Sort=8205

http://www.motortronics.com/products/acdr/acdr_me2.html

Quando Omni Flunkus Moritati

 

[peebee]

There's reversible 120-volt 1-phase fans out there, why don't you hack one of them and see how they do it? Maybe you can just buy a similar motor to those fans?

 

[peebee]

Here's another thought -- most cordless screwdrivers use planetary gears for reverse (thanks to howstuffworks.com for info on both cordless screwdrivers and planetaries), maybe a planetary is what you need.

 

[jbartos]

Suggestion to njlee (Mechanical) Jul 3, 2003 marked ///\\Are there ways to reverse a regular single phase fractional hp AC motor?
///Yes.\\ I think switching the wires will not do it.
///Switching the wires over the switch is usually done. If there is any reason not to do it this way, then there must be motor power supply source that provides the proper commutaction of power supply with respect to motor leads.\\ Can I do it by using additional hardware (switches or controller or ...)???
///Certainly.\\ Or Do I have to get special kind of motor.
///The motor must have provisions for being capable of operating in both directions of rotation.\\\