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plk
Premium
join:2002-04-20
united state

Old electric motor wiring question.

Hey mod, please move this if wrong forum.

I have a old huge and heavy electric motor I want to see if she will run. They don't make them like this anymore.

Anyway. I can't ID the colors of the wires. It will run on 110 or 220v.
It has 3 coming in and 4 inside the motor. 2 of which connect to one of the 3 coming in. So I have 4 poles and two are bridged. Make sense?

spec's
Century Repulsion start induction
Single phase
Type rs
frame 224
model sda 7997
HP 1.5 hp
110v or 220v
18.6 amp or 9.3
RPM 1750
Ser d30975

I looked inside and it has a back plate that looks like brushed, but I dont think they touch. Never seen this type before.
Any of you folks know these old motors? Or what the wire sequence is?



No_Strings
Premium,MVM,Ex-Mod 2008-13
join:2001-11-22
The OC
kudos:6

Let's try Electronics. Based on the knowledge base there, I think it's the best fit.



Kringle
Dr.D
Premium
join:2004-02-27
Pierrefonds, QC
kudos:3
reply to plk

This might give you some info: »www.practicalmachinist.com/vb/ar···312.html

I do think you'll have to give A. O. Smith a call for the complete data though.



John Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
kudos:5
reply to plk

Pics would be helpful...
--
A is A



drjim
Premium,MVM
join:2000-06-13
Long Beach, CA
kudos:3

1 edit

2 recommendations

reply to plk

You have a TWO pole motor. The speed on the nameplate is the giveaway. Theoretically, a 2-pole motor would run at 1800RPM, but since an AC motor has to 'slip' to develop torque, it runs at 1750RPM.
"Repulsion Start" is explained here:
Repulsion Start - Induction Motors. The repulsion start induction motor is a single phase motor consisting of a stator winding connected to the power source and a rotor winding connected to a commutator. The motor starts as a series motor and at a predetermined speed, all the commutator bars are electrically shorted by a device called a "necklace" to give the equivalent of a squirrel cage winding. This type of motor starts as a repulsion motor but operated as an induction motor with constant speed characteristics. It does require more maintenance and has therefore been almost entirely replaced by capacitor start motors, although the repulsion start induction motor can develop more locked-rotor torque with much less locked rotor current.
Courtesy of: »www.sdp-si.com/D220/HTML/D220T145.htm

This is very similar to a "Wound Rotor" motor, only instead of using the rotor windings to control the speed, they're used as a starting winding, and then shorted together once the motor reaches its "Base Speed", identical to what the controller of a Wound Rotor motor would do when running at full speed.

And yes, if it's Repulsion Start, it is quite old!
--
One man's Magic is another man's Engineering.



Kringle
Dr.D
Premium
join:2004-02-27
Pierrefonds, QC
kudos:3
reply to plk

By the way, this is the contact page for A. O. Smith: »www.aosmithmotors.com/html/contactUs.html



Bill Howland

@verizon.com

1 recommendation

reply to drjim

Actually, if its 1750 rpm @ 60 hz its a 4 pole motor; a 2 pole motor on 1-phase 60hz is 3450 rpm (sync speed 3600).

All the references to A.O.Smith won't help much, since they purchased Westinghouse's (the predecessor company prior to AOS (basically a water heater company) small motor division, along with magnetec, and Century. They don't currently sell a Repulsion - Start, Induction - Run motor, and haven't for years.

Anyway, to get it to do what you want, if you want 220 volts hook the 2 middle wires in series. If you want 110 volts, just hook up 1 and 2 to one leg, and 3 and 4 to the other...

The really cool thing about "R-I" motors is they will start and run on 1/2 voltage, so if you're still unsure, wire it up for 220 volts but plug it in on 110. The 1 1/2 horsepower motor will start and run at normal speed but will only have a 'full - load' rating of 3/8 horsepower.

Those old century RI motors are amazingly efficient. 19.6 amps on 110 volts for a 'non-power-factor-corrected-true-single-phase-1.5 hp-motor' is almost unbelievably efficient. Starting current is super low too, considering the huge locked rotor torque the thing developes. People always throw them out because they think all those circles in the frame are ugly, and its 'too heavy'. I think they are marvels of early american enginneering and I'm sorry that we can't buy such a great motor today.



Kringle
Dr.D
Premium
join:2004-02-27
Pierrefonds, QC
kudos:3

said by Bill Howland :

All the references to A.O.Smith won't help much, since they purchased Westinghouse's (the predecessor company prior to AOS (basically a water heater company) small motor division, along with magnetec, and Century. They don't currently sell a Repulsion - Start, Induction - Run motor, and haven't for years.
A. O. Smith has documentation on all of the old Century motors and I've been told (by a reputable source) that they will send it out on request. They may even have a .pdf scan of the required docs that could be sent by e-mail.