Interesting old Motor 2

[roydm]

Over the weekend I passed through Greenwood BC, there in a park was an ancient Ingersol Rand No 10 compressor hooked to a 3 phase alternator. At first I thought the compressor was a steam engine since it had mechanically activated valves.
The electrical machine was a wound rotor with large solid iron pole pieces with no windings, just a simple copper bus-bar. and seemed to have been built in 1898
I assume the windings were taken off at some stage and the generator converted to a motor.
I can't imagine it was too efficient. Was this common practice?
It had a clutch, I assume it was bought up to speed then engaged like a ball mill.

 

[waross]

The windings have probably been stolen from the solid pole pieces.
If the pole pieces are solid, the windings would have been DC. This may have been a synchronous motor.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[jraef]

Looks like a synchronous motor to me too. The red coated stuff looks like the amortisseur winding, used to get it to speed before energizing the field. That would be copper too, not not as obvious. In a lot of old unused motors like that, copper windings were stripped out during WWII (those that survived were stripped a few years ago by copper thieves). I used to see a lot of old big motors like that in abandon mines in the Sierras in the 60s and 70s. When the mines played out, it was too expensive to move the now worthless machinery. My father told me they would have copper drives during the war and local women would go out in the old mines and abandoned lumber camps to get the copper, my Aunt was one of them. They were often unaware of other copper sources they couldn't see, or unable to remove it if even if they did. Big exposed motor windings like that were easy targets.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[ScottyUK]

I'll take a contrary view. Unusual for me to do that isn't it?

The spoked spider and built-up rotor indicate that the machine is a low speed type. The bright red section is the winding of the rotor, and behind the dull red of the coupling in the foreground are three sliprings and the rusty remains of the collector. Three rings suggest an AC induction machine rather than a synchronous type with a DC field which would require only two. The radial connections on the spider appear to be at 90° intervals which perhaps suggests there are four connections to the rings but I can only see three sliprings.

Do you have any other images which show the rings more clearly?

 

[roydm]

Yes it has just 3 slip rings, I took a picture of the nameplate but it's very hard to make out but this is what it says to the letter (I left most of the patent Nos off)

Westinghouse Elec. & MFG CO
Pittsburgh PA
Constant Potential Alternate Current Generator
Patented
Stanley Sept 21 1885 NO 349615
Schmid May 29 1888
Westinghouse ETAL Dec 13 1887
Stanley May 29 1888
Shallenberger May 29 18888
Schmid May 29 1888
Schmid July 9 1889 NO 406858
Other Patents Applied For

No 98445 514 Rev.
3 Phase 236 Amperes (could this have been 23.6 Amps) 440 Volts

I'm sure it must have had some field windings at some time but given the poles are solid and it has some shorted out bars next to the rotor you don't think it could have been run like that?
Is it possible Tesla could have had a hand in it
s design?

 

[roydm]

Here is a picture of the whole compressor, ignore the small one on the right

 

[jraef]

SottyUK, I think you are right. I failed to catch that the thing I thought was the amortisseur winding is on the rotor, not the stator. 3 slip rings confirms it, you would only need two for a synch motor.

Must be a "doubly fed"* induction generator then. That's basically a Wound Rotor Induction Motor configured as a variable speed induction generator. It's a very old technology that fell out of favor, but has resurfaced again as a popular choice for Wind Turbines.

*aka "double feed"


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[waross]

The nameplate says "Constant Potential Alternate Current Generator ".
The field is stationary. The solid pole pieces strongly imply DC.
What looks like an amortisseur winding is on the stator. You can see the bolts holding it on. I suspect that it was a retainer for the field windings.
I have run into more than one old alternator with a stationary field and the load current taken off through slip rings.
This may be an alternator repurposed as a synchronous motor, or the "compressor" may actually be a steam engine.
Probably a steam engine. The machine may have difficulty starting as an induction motor with the salient poles. It could start as an induction motor if a squirrel cage winding was fitted to the stator. The device that I suspect is a retainer for the field windings would not function as a squirrel cage winding. The bolts may overheat and there are probably not enough of them to act as a squirrel cage.
I don't like going head to head with two Gurus whom I respect, but I have seen too many alternators with stationary fields.

Here is a link to some pictures of an old Onan, circa 50s or 60s
This has a stationary field and both AC and DC windings on the rotor. The DC winding is used for field current, battery charging and possibly starting. Some similar models have used the DC winding for starting but I don't know about this particular model.

http://oldengine.org/members/diesel/Onan/OnanMenu4.htm

This is a single voltage 230 Volt machine, hence two slip rings.
I have seen newer Onans with two 115 Volt windings and four slip rings for either parallel or series connection for 115 Volts or 115/230 Volts.

Here's an old Kohler with a stationary field;
Page 27 shows the stationary fields, the slip rings and the commutator.

http://www.oldengine.org/docs/kohler_LP_OM.pdf

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[ScottyUK]

Roy / Bill

That makes sense. We have become used to alternators with a rotating field and the main output from the stator but originally the field was stationary and the main output was from the rotor. As machine outputs increased in current and voltage the field was moved onto the rotor because of the limitations of the collector gear.

 

[LionelHutz]

I agree with Bill. It's an "inside-out" synchronous machine. I don't deal with generators very often, but I recall one tractor driven generator built like that.

 

[roydm]

Thank-you for the interesting comments, I especially like the description, "Inside out" synchronous machine. I don't think I have seen another wound rotor motor where the main winding was on the rotor.
I printed out one of the patents where they claimed a feature was the ability to be able to lift the rotor out in one piece by splitting the frame in half. As an apprentice I was fortunate to work on Ward Leonard and Schrage motors and quite a few other weird DC machines.
I first thought the compressor was a steam engine because it had mechanical rather than pressure operated valves but it turns out the Ingersol Rand model 10 was quite a common machine around the turn of the century.
It was either used for driving underground drills or perhaps blasting air into the copper smelting furnace.
Cheers
Roy

 

[waross]

The machine may have originally been driven some type of hydro turbine or steam engine.
When it was put on display, the compressor may have been more interesting than the original drive machine and so was used instead of the original prime mover.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[LionelHutz]

It likely could be used as a motor. You can see amortisseur winding or a squirrel cage built onto the DC pole faces so it should be able to start as an inductive machine.

Would it have been 25Hz and 214rpm?