2 speed electric motor starting

[gd6844]

Gooday,
Ihave a problem with a client who has purchased a second hand 30 year old butchers meat grinding machine.
The machine has a 60HP 2 speed motor which has a star delta
starter.The starter has a low speed and high speed function.
The original means of startup was to run up oan s/d start to
run and then switch to high speed via the 2cnd winding of the motor.Unfortunately some person altered
the
control wiring for one reason or another to start the motor
in the high speed mode which resulted in the motor rotor
disintegrating.The original purpose built starter is a
Sprecher & Schuh.Would someone out there have a schematic
wiring diagram or a clue as to how this system works.In40 years have not had an experience with a 2 speed star delta
motor starter.Any feedback would be greatly appreciated.
Thanks & Regards,
Graeme de.Araugo.

 

[jbartos]

Suggestion: Visit

http://www.ssusa.cc/pages/mainpg/prodmainall.html

http://www.ssusa.cc/pages/mainpg/librmainall.html

http://www.ssusa.cc/reference/wiring_diagrams/standard_series_drawings/series_109/109_01.pdf

etc. for more info

 

[Laplacian]

If it's two speed, it's not star/delta wound. It's probably a 8 pole motor wound on 4 poles for the high speed configuration - 900 rpm base, 1800 rpm high speed (15/60HP).

We have some old GE cooling tower fan motors configured like that with the original GE starter. It has a special TDUV type shutdown scheme which you may not need.

The starter utilizes 3 contactors for operation. A low speed, high speed and tie contactor. The tie contactor shorts the three phase leads together on the "slow" windings after the "fast" button has been pushed.

Two interposing relays are used to pick up the contactors; one for "slow" and one for "fast". If my computer wasn't broken at home, I'd sketch a little diagram .

If you're familiar with a standard motor starter, it is easy to wire up (start up in slow mode first):
Start for slow speed picks up the interposing relay for the "SLOW" contactor. ("FAST" interopsing relay/contactor deengerized)

Start for fast speed picks up the interposing relay for the "TIE" contactor and opens the circuit for the slow interposing relay coil via another set of contacts on the pushbutton. The "TIE" contactor has an auxiliary set of contacts that pick up the "FAST" contactor.
(there is a mechanical interlock to prevent the tie and slow contactors being closed simultaneously). You could use a permissive set of contacts off the "slow" interposing relay in the TIE contactor coil circuit.

There is a common stop pushbutton that interrupts control power to the control circuit.

 

[Marke]

Hello gd6844

There are a number of different two speed motor configurations.
The one that I am most familiar with is essentially a delta double star. This would generally be a 8 pole - 4 pole, or a 4 pole - 2 pole setup, i.e. a 1 : 2 speed change. This configuration can also be used for a PAM wound motor. (Pole Amplitude Modulated) and this can do a 6 pole - 4 pole speed change.

With the delta double star configuration, the low speed connection is as a delta connected motor. Each leg of the delta has a center tap. For high speed, apply the supply to the center taps of the windings, and tie the delta apexes together. This in effect creats two stars in parallel, and hence the name delta double star. The motor rating in high speed is much higher than in low speed, I think from memory, it is in the order of four to one but I would need to look that up.
An example of a delta double star starter can be found here :

http://www.ssusa.cc/reference/wiring_diagrams/standard_serie

s_drawings/series_110/110_01.pdf

Best regards,

Mark Empson

http://www.lmphotonics.com

 

[cbarn24050]

Hi Gd, last time I worked on one of these it was a PAM motor (9 leads) if that is what you have then it's fairly simple to do. You should be able to find a diagram in any motor wiring book. If I were making a new one today i would use a micro PLC to control the contactors. You should have 4 power contactors, 3 connect to the low speed winding (6 leads) in the standard star/delta fashion and the last connects to the high speed winding(3 leads) dol. To start in low speed is as you would expect, to go to high speed you drop out the low speed line contactor, close the star contactor and the high seed contactor.

 

[jbartos]

Suggestion: It would be very considerate to post the motor nameplate data to make sure that there is not any ambiguity in wording and that the motor is traceable.