Schrage motor's

HJTRBO · Dec 13, 2010

Hey all,
Came across a Schrage motor today. I had to wire in a replacement (same for same as the old one luckily!). I've got no idea on the principals behind them. I'm doing the google thing at the moment trying to work them out.
The motor we put in was 55kW 600 - 2200 RPM 380v Delta.
Can someone give me a Shrage 101?
Cheers, Nathan

DickDV · Dec 13, 2010

These motors are marvels of engineering, acheiving variable speed AC with multiple brushes mounted on rotatable rigging and little servo motors to control the rotary position of the brushes.

For a real description of how these things work, I suggest you post this question on www.eng-tips.com. Choose the "electric motor and controls" bulletin board. There are some international motor experts on there that can give you a detailed explanation. (Maybe too detailed!)

While they work very nicely, you will break the bank trying to repair them. Clever, inovative, unique, but not very practical.

HJTRBO · Dec 21, 2010

Thanks for refering me to the other site.

I found this there. Man, there is very little information out there that's for sure.

Cheers, NP

BobB · Dec 21, 2010

I have not seen one of those since the 60's!!! Used to repair and rewind them.

HJTRBO · Dec 22, 2010

BobB said:
I have not seen one of those since the 60's!!! Used to repair and rewind them.

We've got 4!

You wouldn't happen to remember how they work in laymans speak would you?

I've got another one that sometimes pulls 50 - 55 amps on the secondary winding's and it's only rated for 48. Occasionally (as expected) we get the internal overload(s) tripping.

504bloke · Dec 22, 2010

Quite a good explanation from the net

Factory I do work for has a few still, the machines they are on are Swedish which is where the schrage motor was developed I believe

The Schrage motor is a polyphase Commutator motor with shunt characteristics, it has a wound rotor. On the rotor, there is a three phase delta winding with the endpoints of the delta brought out on to slip rings. The three phase supply is connected to these slip rings. Also on the rotor, there is a second delta connected winding with tapings brought out to a commutator. On the stator, there are three discrete windings separated by 120 degrees. The ends of these windings are connected to the commutator by two sets of brushes such that one set of brushes connects to the starts of the stator windings and the other set connects to the ends of the stator windings. The two sets of brushes can be moved to connect to the same point on the commutator, or moved apart in either direction. When they are in alignment, the stator windings are shorted and the motor behaves like an induction motor with the rotor and stator swapped. As the brushes are separated, voltage from auxiliary rotor winding is coupled to the stator winding. The degree of separation and the direction of separation varies the voltage and polarity of the voltage. The frequency of the voltage applied to the stator is dependent on the slip.
In effect, the stator has an induced voltage from the slip, plus a driven voltage from the commutator. This causes the speed of the motor to change. Speed variations of up to 10 to one are possible and the motor can provide a high torque at all speeds.

BobB · Dec 22, 2010

Is the machinery extruders ex Cable Makers Australia? That is where I became familiar with them. Along with Lawrence Scott Electromotors Triplex armature windings with a commutator at one end and slip rings at the other - double tough enamel insulated bars in the armature and concentric GE type winding in the stator - mongrels to wind by the way but it was a way of getting good torque at all speeds rather than a 'peaky' torque as with most motors.
I am afraid my memory of them is a bit vague - 1960s and now have 'old timers'. They work on a variable brush position and angle - a small wheel to adjust the speed if I remember correctly - that is about all I can remember - apart from the fact that one of the guys was working on one - brushes were pretty worn out - sparking like an SOB - Shell X55 solvent under the bench with the lid off!!! I tackled him alight at the loading dock and one of the other guys threw a pile of rgas over both of us to put the flames out!!! Still have the scars.
We used to use a brake and pulley attached to a spring weigher attached to an overhead crane to check the torque!!!
Could tell many stories - some pretty unbelievable but not now.
You may be able to find an old fella in a winding shop (if you can find a winding shop) that may remember better than I.

HJTRBO · Dec 22, 2010

...brushes were pretty worn out - sparking like an SOB - Shell X55 solvent under the bench with the lid off...

haha! Classic Aussie bloke's right there!

The machines are Alpine single layer rotating blown film extruders. The motors have the brush positioner motor with the cam switches and relay logic.
504 cheers for finding that explaination, that's alot easier to understand than the others I have read. I almost have got it. I need to spend an hour or two on the motor with the covers off doing some tests to get it all to gel together.

BobB · Dec 22, 2010

Just be careful of the X55 under the bench.
And then there was the turps bay - minerla turpentine in a big tank with a wash bay over the top and a high pressure pump for cleaning motors, beartings, rotors, shafts etcetera.
The there were the carbon tetrachloride fire extinguishers - brass tube type with a pump. they used to use it for cleaning carpets and could not work out why capet cleaners were dying. Turned out they would clean carpets all day, have a beer on the way home and the alcohol and carbon tetrachloride made a poisonous combination and killed the carpet cleaners.
they also used to use carbon tetrachloride for dranching sheep. Used to pour it straight down the sheeps throat.
The good old days!!!
Soryy to hijack the thread - just a few old memories. No MSDS sheets in those days.

504bloke · Dec 22, 2010

BobB said:
Is the machinery extruders ex Cable Makers Australia? That is where I became familiar with them. Along with Lawrence Scott Electromotors Triplex armature windings with a commutator at one end and slip rings at the other - double tough enamel insulated bars in the armature and concentric GE type winding in the stator - mongrels to wind by the way but it was a way of getting good torque at all speeds rather than a 'peaky' torque as with most motors.
I am afraid my memory of them is a bit vague - 1960s and now have 'old timers'. They work on a variable brush position and angle - a small wheel to adjust the speed if I remember correctly - that is about all I can remember - apart from the fact that one of the guys was working on one - brushes were pretty worn out - sparking like an SOB - Shell X55 solvent under the bench with the lid off!!! I tackled him alight at the loading dock and one of the other guys threw a pile of rgas over both of us to put the flames out!!! Still have the scars.
We used to use a brake and pulley attached to a spring weigher attached to an overhead crane to check the torque!!!
Could tell many stories - some pretty unbelievable but not now.
You may be able to find an old fella in a winding shop (if you can find a winding shop) that may remember better than I.

Yes extruders, make are Buss

That will be my dad then, old fella from winding shop, hes 74 next year

Schrage motor's

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