INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Member Login




Remember Me
Forgot Password?
Join Us!

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

Join Eng-Tips
*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.
Jobs from Indeed

Link To This Forum!

Partner Button
Add Stickiness To Your Site By Linking To This Professionally Managed Technical Forum.
Just copy and paste the
code below into your site.

SPLIT PHASE START MOTOR

SPLIT PHASE START MOTOR

(OP)
Can I eliminate the centrifugal start switch ( which is broken, cannot find replacement parts) on a 1/2HP motor, with a solid state device such as a Supco R041?

RE: SPLIT PHASE START MOTOR

No. That appears to be an overload protection device. The centrifugal switch is used to switch the starting and running capacitors in the motor. Without that, the motor will not turn. The centrifugal switch has nothing to do with overload protection (other than the fact that if the motor doesn't turn, it overloads!). It shouldn't be too difficult to replace that switch though.

JRaef.com
Eng-Tips: Help for your job, not for your homework  Read FAQ731-376 pirate

RE: SPLIT PHASE START MOTOR

(OP)
The R041 is a start relay/overload device. I have installed them on refrigerator compressors with or without start capacitor. The motor is a Superline Frame A71 Type SP-KR made by Murai Kiki Corp. Japan under licensed by Mitsubishi. I cannot find an any parts suppliers for this motor. The drive dogs for the centrifugal throw out are broken. If you can direct me to a supplier that may have parts I would replace them. If not I will work on a solid state start relay solution. I also have a Supco Starter Pow-R-Pak Model SPP that I picked up at the parts house the other day. I was wordering if a split phase start motor would work with a solid state start device.

RE: SPLIT PHASE START MOTOR

You can use a  NO Contactor to bypass the centrifugal switch. The contactor will be operated by a relay sensible to the line current. It will make with the inrush current and will open when the line current drops to around 150% full load current.Probably you will be able to get the same logic with solid state circuits.

RE: SPLIT PHASE START MOTOR

I had a gas dryer that had the start winding running thru the 'Start Cycle' switch.  You had to turn and hold the switch long enough for the motor to start. Rather like starting a car.  I don't know what was used to latch the motor ON once it was up and running..

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: SPLIT PHASE START MOTOR

Hi Keith;
In a drier the centrifugal switch is commonly double throw.
The normaly open contacts turn off the heat if the motor stops and are also used to seal in the motor control circuit.
This arrangement seems to be unique to motors on clothes driers.
Respectfully

RE: SPLIT PHASE START MOTOR

Ahhh! Thanks waross for that.  Makes total sense to how I remember that dryer working.  I was in it all the time.  It was one of those 'fiddling required' models.  It had a buzzer for an igniter that interfered with half the stuff in the house. The contacts burned out constantly, (since they lived in the flame).

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: SPLIT PHASE START MOTOR

(OP)
The RO41 worked fine. The ice shaver is back up and running. Making snow cones once again.

RE: SPLIT PHASE START MOTOR

The centrifugal switch is a clothes dryer also has an additional normally open contact that activates the burner or the electric heating element.

Some of the solid state motor starting relays on the market can self adjust for a particular size motor, partiularly the ones that can add a starting capacitor. A so called hard start kit converts a permanent split capacitor refrigeration compressor to capacitor start capacitor run and uses the voltage across the start winding rather than the current through the run winding.

The classic split phase starting relay was made by Texas Instruments and had the coil in the run winding and a normally open contact for the start winding. These were gravity sensitive and used gravity to open the contact. To get a relay that would work for a goofy size refrigerator motor that was made in Italy I had to get a smaller size relay, unwind all of the winding turns ( 70 ) and then rewind on the number of turns ( 60 ) that would get this motor to work.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Related News

Resources

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close