Reversing induction motor

[Gazzman]

I want to reverse an induction motor (industrial fan, single phase). I've located a site on the net that advises substituting the start capacitor with a choke, specifically the secondary winding of a low voltage transformer. In that case 24v transformer with a 120v supply. I've tried it and the concept works !!

My question is how to calculate the correct size choke (transformer) for a 240v supply. Anybody know of a formula? Thanks if you can help me out.

 

[Knobhead]

Never heard of using a choke to reverse a motor, it sounds feasible. What site was this?

 

[Kenny.]

on the majority of cap start motors, If the motor has 4 leads coming from the stator, you need to identifie the 2 pairs (running winding and starting winding) and reverse either pair (only reverse one of the pairs). if there are more or less leads (split phase or cetrifugal cut-out) take a pic and someone will be able to help.

 

[mnbs 4x4]

from memory dont you swap EITHER Z1 and Z2 OR U1 and U2 being the start winding and the run winding, did it years ago but cant remember for sure, would be alot easier than the transformers etc, remember it will be a 440v cap

 

[mattmoo1974]

Swap start winding or run polarity NOT both.

 

[MarkieSparkie]

By swapping the start capacitor for a choke, you have changed the motor from capacitor-start to reluctance (or induction)-start and as you have found out the direction of rotation is reversed.
However as already stated by others here, the simple way to reverse the rotation of your capacitor-start motor is to reverse either the start winding (Z1-Z2 terminals) or the run winding (U1-U2 terminals), but NOT both. In practice, usually you will have just one pair of winding terminals, either U1-U2 or Z1-Z2, plus the capacitor terminal pair 4-3 inside the motor connection box and this prevents the reversing of both the start and run windings.

 

[Gazzman]

Here's the link

HMSC September 2001 Newsletter

 

[Gazzman]

I'm only messing with this procedure because the start & run windings aren't fully separate. As often happens these days, they have a common connection within the motor, so you see I have only 3 leads to work with, not four.

 

[Gazzman]

I'm only messing with this procedure because the start & run windings aren't fully separate. As often happens these days, they have a common connection within the motor, so you see I have only 3 leads to work with, not four.

 

[Gazzman]

HMSC September 2001 Newsletter

 

[Knobhead]

Thank god their Americans, there’s too many of them anyway.

It’s not the reversing of the motor that would worry me but reversing a grinder or circular saw?

The author must be bloody MAD!

 

[Knobhead]

Deleted

 

[RWJ]

"Joe Scott showed a video on the history of Springfield Armory and gave an interesting talk on chambering firearms and adjusting for proper head space. He also explained the legalities of gunsmithing"

 

[Gazzman]

yep - like they say "only in America".

 

[MarkieSparkie]

I've not come across a 3 terminal connection yet, but thanks to your thread it won't be the head scratcher that it might have been. Thanks again.
What is the size of your motor in horse-power or Watts and what is the value of the start capacitor in micro-farads?