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Discussion Starter · #1 · (Edited)
Iam trying to simultaneously power two 48v traction motors with one battery pack for my miniature train repower. Having no success on line finding a suitable main contactor to connect the two motors and controllers. Anybody know who sells such a thing these days?

alternatively, there’s plenty of DPDT contractors available. But, I am not certain how to wire them for one power source input and two simultaneous power outputs. Is this a viable option somehow??

Thanks much,
Glenn
 

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Don't you need a DPDT for reverse or is that mechanical?

In any case a DPDT has six terminals, you get DPST by simply not connecting two of the thrown terminals.

i.e. power to the two center terminals, then connect to the normally open contacts of the DPDT, assuming you are using the contactor as your on/off switch.
 

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Something like this?

These are what I am using on my conversion project, so far I'm very impressed with the quality. Single hand operation, shielded contactors, really robust construction and stiff cam-lock retention tabs. Kinda hard to get the cam open till you figure out the trick, but I'd rather have it that way than have it likely to pop open by accident. And they shipped almost instantly, got them in a few days with the cheapest shipping option.

They are expensive though, around $100 for the plug and receptacle, for the models I used. i got the straight through style, not the 90* pictured.

121538



There is a ordering matrix to make sure you get the exact correct part number for what you want, there are many styles and options so have the part number just one digit off can change the part completely. My friend wasn't paying attention when he ordered his, got 10 of the wrong receptacles. He opened 4 of them before he figured it out, sent them all back, but they would not accept the opened ones and sent them back to him. It was a pretty costly mistake.
 

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Copy that, read it as connector.

I used the contactor assembly from a Nissan leaf pack. It has two contactors, driven by 12v. You could wire both on the same 12v supply line to shut them simultaneously. I have a second one I don't need, if you can use it I'll send it to you for the cost of shipping.

121540
 

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Discussion Starter · #6 ·
T
Don't you need a DPDT for reverse or is that mechanical?
[/QUOT is a which is separate from the main contractor.
Remy, yes, I do have a separate DPDT for the reversing function. The DPST unit would be a main contactor between the battery pack and two high voltage circuits. With two motors, Iam needing two B+ terminals to feed both controllers and motors.
 

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Uh, maybe I am missing something, but why dont you just use a regular contactor, and connect 2 cables to the one output stud? One wire goes in, 2 wires go out, is that what you are trying to do?
 

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Discussion Starter · #8 ·
Or-Cal, good question. The way I understand it, the two motors and controllers can potentially draw up to 400 apps each. The single pole main contractors are only rated for either 180 or 200 amps. So a double pole contactor, (or separate single pole contractors) is needed to safely accommodate the max current.

(BTW, I’d be very happy to be wrong about this, as my parts list would be a lot less expensive.)

am trying to clarify with Curtis. But so far, they only seem interested in talking to big, industrial OEM’s. These 1209b controllers are old units, very little technical documentation exists these days.

Glenn
 

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400 Amps, even at a modest 48V, is still 19kw of power. So, while it may be possible for the controller to handle that much, are you going to have the traction to to deliver almost 40kw to the rails? Is this going to be a drag-racing train :)? Joking aside, I really have no real world numbers to back me up, but I calculated that my 3300lb truck will need something like 20-25kw to maintain 55-60mph. I plugged some of your numbers into my equation for powering my truck;

Assumptions were: 12,000lbs, 10mph, .02 rolling resistance, .5 coefficient of drag, and frontal area of 1 sq meter.
I came up with 4800 watts. Playing with the numbers, you can basically ignore the wind resistance, and that coefficient of drag is for rubber tires on asphalt, so you could probably get away with much less power.

So... at 48 volts, I am guessing you will be pulling something closer to 100 amps.
 

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T


Remy, yes, I do have a separate DPDT for the reversing function. The DPST unit would be a main contactor between the battery pack and two high voltage circuits. With two motors, Iam needing two B+ terminals to feed both controllers and motors.
You sure about that?

I'm thinking your "B+" goes from pack to contactor and then to two controllers. DPST with both terminals connected on the battery side, then one terminal to each controller. Of course you can use a contactor each between the battery and each controller.

Between each controller and its motor, you have a reversing contactor (assuming your controller does not do polarity reversal).
 

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Discussion Starter · #11 ·
Remy and Or Cal, thanks for reviewing. Well, Iam actually a hoghead- old time steam guy. So learning as I go with this electromotive build. Couple of electrical engineers advised me to go with a DPST main contractor - to wire up the two controllers. So that’s what started me looking to that configuration.

Looks like what you said would work fine. As what I really need is to pin down the connection between the contractor( or contractors) and the controllers.

Particularly as Remy’s numbers are right in the ball park- 100 amp draw for a 12,000# train resistance. This was the key piece I’ve been missing- actual current draw for thismsize locomotive. I did compute tractive effort based on the weight on drivers. So Remy’s numbers and mine closely align - except he calculated power and I did not...

So good to know there are several viable options available to set up the high voltage side...

Thanks much,
Glenn
 

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They weren't my numbers (not shunning the credit, just disavowing myself in case the calcs are way off)

One thing to watch out for here in the Pacific Nortwet is we have a lot of gravity that affects our vehicles, so you need to work max grade speeds into into your power calcs. But, wet thumb in the air says the numbers feel right...hopefully you've got some reduction gearing in play.
 

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Iam trying to simultaneously power two 48v traction motors with one battery pack for my miniature train repower. Having no success on line finding a suitable main contactor to connect the two motors and controllers. Anybody know who sells such a thing these days?

alternatively, there’s plenty of DPDT contractors available. But, I am not certain how to wire them for one power source input and two simultaneous power outputs. Is this a viable option somehow??

Thanks much,
Glenn

Iam trying to simultaneously power two 48v traction motors with one battery pack for my miniature train repower. Having no success on line finding a suitable main contactor to connect the two motors and controllers. Anybody know who sells such a thing these days?

alternatively, there’s plenty of DPDT contractors available. But, I am not certain how to wire them for one power source input and two simultaneous power outputs. Is this a viable option somehow??

Thanks much,
Glenn

What about something like this?

 
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