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3 - terminal centrifugal switch ????? #178521 06/03/08 01:17 PM
Joined: Jun 2008
Posts: 5
MotorMutt Offline OP
New Member
We have a Doerr-Emerson Class B 115/230 V, 1 ph, capacitive start motor. Not much left on the name plate, & no wiring schematics.

The centrifugal switch has 3 wires going to it, not 2 as shown in a typical "generic" Cap Start motor schematic. One wire from this switch goes to the cap, the other two wires go to two external leads outside of motor.

We want to run this on 115 V, rotation direction not critical.

Can somebody fill me in about how this switch works with the three wires?? Does it act as a SPDT switch?

Work Gear for Electricians and the Trades
Re: 3 - terminal centrifugal switch ????? [Re: MotorMutt] #178556 06/04/08 02:52 PM
Joined: Jun 2007
Posts: 301
JValdes Offline
I am looking at a drawing of two single phase motors, one is dual voltage and the other is single voltage. The switch on both is wired the same.
On both motors the switch and cap are in series with the aux start winding. Numbers 5 & 8. Here is the connection directions for both motors.

Single Voltage
CCW - L1 - 1 & 8 L2 - 4 & 5
CW - L2 - 1 & 5 L2 - 4 & 8

Dual Voltage
High CCW - L1 & 1 L2 - 4 & 5 Join 2 - 3 - 8
Low CWW - L1 & 1 - 3 - 8 tied L2 2 - 4 - 5 tied.
To reverse direction interchange 5&8

#5 goes directly to the switch then to the cap and then through the start winding and leaves the motor as #8.
#5 should be Black and #8 red.

The wires that are in the pecker head should be marked or color coded. Here is the legend.

1- blue
2- wht
3- org
4- yellow
5- black
6- NCA
7- NCA
P1 - NCA or brwn
P2 _ NCA or brwn
Note: NCA No Color Assigned.

Are the leads marked or colored?
Check the switch and see which two wires are opening and closing, use those two wires. Tie off the other. Then connect using diagram or legend above. If they both switch use just one.

The switch opens thecircuit to the start winding when the motor reaches full or close to full speed.

If you cannot figure it out, your local motor shop can help you. Just call and ask how to connect.

Ps....I don't know why the numbers above are bunched together and hard to read. I have tried a couple times to seperate them with no success. I hope you can make them out.

Last edited by JValdes; 06/04/08 03:00 PM.
Re: 3 - terminal centrifugal switch ????? [Re: JValdes] #178560 06/04/08 04:50 PM
Joined: Jun 2008
Posts: 5
MotorMutt Offline OP
New Member
Thanks, JV - Yes, I've seen that diagram you refer to and it shows a simple SPST switch in series with Cap. Since I posted yesterday,I've found more info (The motor is about 1,000 miles away & I'm not sure if the chap I'm helping even has an ohmmeter...yikes!)

We think this trolley motor is wired internally to receive 110VAC single voltage only, because of my next sentence.

There are two run windings in parallel; one pair of winding ends are marked T1 and T3, the other winding ends are marked T2 and T4. These are brought out of the housing with a Black wire (T1 and T3) and a Red/Black wire (T2 and T4).

The one end of Start winding marked T5 comes out of motor with a White wire; the other end of Start winding is marked T8 internally, and goes to one side of Cap. The other wire from Cap goes to what is correctly called the Stationary Switch and is marked J "something", can't quite tell what it is.

Also from the Stationary Switch come two wires; one is labled J10, the other is labled J11. J10 comes out of motor with a Red wire, J11 comes out of motor with a White/Black wire.

There is also an external Blue wire and Orange wire which go to "Thermostat"; I'm assuming the thermostat is buried within the stator and is to be wired in series with L1 ???

I'm not too keen on external wire colours; they can be unique to the actual motor. I included them here on a whim they'd be useful. Sorry for the long post, wish I could plant a drawing in here.

'Tis always best to quit when you're through


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