Controlling separate DC traction motors

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Steggy
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Re: Controlling separate DC traction motors

Post by Steggy »

John Hasler wrote: Wed Jan 20, 2021 9:05 pmPutting the motors in series would be an elegant solution but it would require a single 96 V controller which you don't have so it's not really an option.
Does a 96 volt controller even exist?
If you do go that route I suggest using contactors with 24 V coils and connecting the coils in series. That way if one coil goes open you just can't reverse.
That would work insofar as it would guarantee that both contactors' coils be in the same state. It doesn't consider mechanical malfunctions, however. The four form-C setup would be best. Absent that, I would be looking for a way to mechanically interlock the contactors to guarantee consistent operation.
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Re: Controlling separate DC traction motors

Post by Glenn Brooks »

Thanks very much John. Big learning curve for me, but more fascinating the deeper I go. I’ll go with the single unit for both motors. The 400 amp contractors are widely available, and low cost, thanks to the golf kart industry... so good to go! I’ll be ordering parts tomorrow!

Thanks much,
Glenn
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Re: Controlling separate DC traction motors

Post by John Hasler »

BigDumbDinosaur writes:
Does a 96 volt controller even exist?

Controllers to run similar sized AC motors from 96 VDC are readily available. I don't know of any offhand for series DC motors but they would be simpler than than ones for AC motors. IGBTs with the required ratings are off the shelf items.

Academic, though.
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Re: Controlling separate DC traction motors

Post by Glenn Brooks »

John Hasler wrote: Wed Jan 20, 2021 11:24 pm Does a 96 volt controller even exist?
Yep, I found several EV DIY (Electric vehicle) vendor’s that produce some very nice DC controllers for automotive conversion, that will handle up to 144v. They are quite expensive though - $2000-$4000 each.

Altrax and Manzanita Micro are two high quality DC controller names. also work with Lithium battery packs.

Price point beyond my old yard goat capability,unfortunately.

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brandon
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Re: Controlling separate DC traction motors

Post by brandon »

I have a not so hypothetical question based on the discussion of series vs parallel, slipping and # of controllers.

If two motors were being used on a single truck, and both axles were chained together such that both motors and both axles moved together or not at all, what would be the best way to wire motors and with how many controllers?

1) Series with 1 controller
2) Series with 2 controllers
3) Parallel with 1 controllers
4) Parallel with 2 controllers
5) Don't do this
6) Other?
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Re: Controlling separate DC traction motors

Post by Bill Shields »

Anyone look at how they did this in the GG1?

They had separate motors on each axle and IIRC were capable of running in either series or parallel depending on speed required.

Of course this may be the big $$$$$ path...but given that they were running in the 1930's -> there may be some ideas buried in the antique tech.

Has anyone suggested using a cheap encoder to measure unequal axle speed and feedback current accordingly? Something similar to what is used in traction control / ABS auto systems?
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Glenn Brooks
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Re: Controlling separate DC traction motors

Post by Glenn Brooks »

brandon wrote: Tue May 04, 2021 5:29 pm I have a not so hypothetical question based on the discussion of series vs parallel, slipping and # of controllers.

If two motors were being used on a single truck, and both axles were chained together such that both motors and both axles moved together or not at all, what would be the best way to wire motors and with how many controllers?

1) Series with 1 controller
2) Series with 2 controllers
3) Parallel with 1 controllers
4) Parallel with 2 controllers
5) Don't do this
6) Other?
Iam not an expert on electric power by any means, but have been told that running two motors on one truck, with one controller is possible, if the controller is configured for that. I think I am correct in that 4QD controllers will do that also, if the motors are within the 4QD power range. Some commercially available programmable controllers can also do that as well.however most controllers with this capability are built for large EV road capable vehicles. So likely outside the size and price range for most live steamers.

Also, I think I am correct in saying typical 7.5” ga electric locos mostly all have individual chain drive from motor to axle. no trucks, that I am aware of, have two motors on a truck, one for each wheel, with both axles chained together.

I have seen a design where two motors mounted side by side, drive a single drive axle, leading to a powered truck. However, that is a different configuration that you describe.

What people have generally advised me is that similar motors on the same truck may turn at slightly different speeds, but, the weaker, or slower of the two, will compensate for the speed difference by operating a little bit faster, essentially matching the speed of the other... this may be the best answer to your question.

I’ll know more in a month or two when I get my center cab finished. It will have two forklift traction motors, with separate controllers, one for each hood end. I plan to test dual motor operating capacity to see how they work in tandem.

Glenn
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Re: Controlling separate DC traction motors

Post by Bill Shields »

I have seen units with 3 axle trucks with 3 motors.

Came to my attention because one axle was running opposite to the other two...loco did not pull worth a hoot. Corrected wiring for fellow and problem went away.

Did not pay much attention to control but was one control for 6 motors.
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Bill Shields
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Re: Controlling separate DC traction motors

Post by Bill Shields »

Ok...whick model and approx $?
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