ECN Forum Forums Technical Discussion Electrical Theory and Applications Single phase inductive motor

Greeting to all, I just found this great site and WOW - lots of good stuff here indeed!

I have a 1/6th HP 115 VAC motor made by Hubbel, model MC42-1003. The single cap is 25 - 30 MFD @ 330 VAC. It has no centrifugal switch inside to open the start windings once it's above the usual 75 - 80% speed.

Now - just what type of motor is this? Cap Start? PSC? Does it have Start & Run windings? If in fact it does have Start and Run windings, what removes the Start windings from circuit once the motor is up to full speed?

I've found on this site very good info on motors that typically have a centrifugal switch, but this motor & how it works is an odd duck to me. Thanks

I think that's an actuator. The capacitor stays in the circuit.

twh - yes, the motor is an "actuator"; it's from a hospital bed. So the cap & start winding just stay energized in the circuit as long as motor is running?

That is a three wire motor with a neutral, a forward lead and a reverse lead. The capacitor is connected between the forward and the reverse leads and stays in the circuit. Energizing the forward lead puts the capacitor in series with the reverse winding; and, energizing the reverse lead puts the capacitor in series with the forward winding. It's a nice way to change directions with a spdt switch or relay.

The capacitor can be built-in or remotely mounted. Just from memory, I think the limit switches occupy the same space as the capacitor - in the motor box with the leads. There is only room for one or the other, so if the capacitor is in the box, the limit switches must be separately supplied.

MotorMutt

Welcome to ECN!!!

Sounds like the Motor is a Permanent Split Capacitor (PSC) Motor, as there is no Centrifugal Start Switch, and there is a Capacitor involved.

If there was no Capacitor or Start Switch, then the Motor would be either a Shaded Pole, Repulsion Start, or some variety of Commutator Motor.

Anyhow, to describe the PSC Motor's function, the Start ("Auxiliary") Winding + Run ("Main") Winding are always connected to the Circuit thruout Start and full speed Run. No Start Switch is included.
The Current through the Aux. Winding is limited by both the Impedance of the Aux. Winding, and the Impedance of the Capacitor.

There are some PSC Motor Schematic in the Technical Reference section, however these Drawings are describing the arrangements typically used with Ceiling Fans - there is an Autotransformer included with the Motor Windings.

Here is one of the Schematics for your references:



Figure 1: PSC Motor with Intregal Autotransformer.

Link to that page:

Schematics For 1Ø Split Phase Motors, Series 3

https://www.electrical-contractor.n...showflat/Number/148744/page/2#Post148744

I will draft up a Drawing of the PSC Motor without the Autotransformer winding, and with Forward / Reverse Controls via Switch or Contactor.

Will let you know when this is posted.

Scott

Just an FYI:

I posted some new PSC Schematics in the Technical Reference Section.

Refer to this topic:

PSC Motors - Schematics

I also "Linked" this thread from the above referenced topic, for discussion purposes.

Scott 35

Thanks for the welcome, Scott. AND the schematics. An auto-transformer on a ceiling fan? Who'd a thunk it? I thought they just used different stator windings for speed control...

Glad the drawings were useful!!!

Scott

Dude,
Your diagrams just keep getting better.
I take my hat off to you.

Mike,

Thanks for the kind words!

AutoCAD and Paint Shop Pro do most of the work on these drawings, and notepad takes care of the text.

I just move the mouse around, hit some keys, and copy/paste text.

I will pass on the compliments to those 3 applications!

Seriously though, thanks for the message!

BTW:

Do the drawings with the Black Backgrounds appear better than the older ones with the White Backgrounds?

The reason for the change to Black Backgrounds is because I now use Black Backgrounds in both Model Space and Layout Space, within AutoCAD - whereas a few years back I had Model Space in Black, and Layout Space in White.

My Eyes are thanking me daily for the change!

Scott