New Machine Build: Bridgeport R2E4 Series II

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02 Aug 2018 20:42 - 03 Aug 2018 18:32 #115437 by tightmopedman9
Been purchasing parts and slowly gutting the cabinet for a couple days now. For now I have a 6i25+7i77 on a ASRock J1900; I don't think I'll need any more IO than what the 7i77 provides. I originally wanted to retain the stock servos, but I couldn't get the machine to run properly in its' original configuration so I abandoned that idea and bought 3 x AMC 30A8s. I'm changing the out the factory Heidenhain ERO 120 500ppr encoders for 1000ppr E5 encoders from USdigital.

I'm keeping the cabinets and power supplies for ease of wiring, but I've run into a slight problem trying to reconfigure the servo amp transformer. It is a multitap single phase transformer with instructions on how to wire for 208V, 230V or 460V. The stock servo amps were run at 128V, but the 30A8s over voltage fault at 86V. The lowest voltage I can get at the DC bus is 90V, unless there is another way I could wire the transformer. I played with a few configurations, but got hesitant on experimenting when one configuration resulted in a quite hot, and somewhat smelly, transformer.

I've attached a picture of the transformer, does anyone have an idea of how it may be wired differently to reduce the voltage between 11 and 13? I need a reduction of about 15-20V.

From the manual this is the description for wiring

208V: Term 1 to Term 5, Term 2 to Term 6; IL1 to Term 1, IL2 to Term 2

230V: Term 1 to Term 5, Term 3 to Term 7; IL1 to Term 1, IL2 to Term 3

460V: Term 3 to Term 5; IL1 to Term 1, IL2 to Term 7

I believe the configuration that overheated the transformer was:
Term 1 to Term 5, Term 3 to Term 8; IL1 to Term 1, IL2 to Term 4
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Last edit: 03 Aug 2018 18:32 by tightmopedman9.

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02 Aug 2018 21:34 - 02 Aug 2018 21:39 #115448 by tommylight
That is a two phase transformer, and can be wired to single phase very easy. I need to see under the wires, but i am fairly certain that if you want to get the lowest voltage from it you have to wire term.1 to term.5 / and/ term.4 to term.8, then connect L1 to term.1 and L2 to term.2 .
After a second look, if you really need low voltage, wire the term.4 to term.5 then connect L1 to term.1 and L2 to term.8. That will be as low as it can go.
Last edit: 02 Aug 2018 21:39 by tommylight. Reason: added more info

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02 Aug 2018 21:54 #115452 by tightmopedman9
I typed out what is under the wires, which is also repeated in the manual.

I wired it like you suggested and it raised the voltage to 105.

To lower the voltage wouldn't you want to move IL1 and IL2 closer to the interior?

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02 Aug 2018 22:16 #115457 by tommylight

To lower the voltage wouldn't you want to move IL1 and IL2 closer to the interior?

That is very wrong.
Did you try the second version ?

The reason you got lover voltage when you did your combo is you had it wired with one of the windings on the wrong side so it was acting as a load, quite powerful load as you noticed by the smell and the heat created.
There are very strict rules for wiring transformers, the good thing is there are very few rules, as a transformer is a simple thing. The main thing is winding start and end, current flow and in no way reverse the polarity of the parallel connected windings, that makes a nice short circuit.

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03 Aug 2018 18:31 - 03 Aug 2018 18:34 #115540 by tightmopedman9
I tried your second recommendation, I didn't originally see it since I read your post in an email and it was truncated from that copy. I was able to get a much lower voltage than needed, but after playing around with it I was able to get 79.8V-79.9V with IL1 to term 1, IL2 to Term 7 and Term 3 to Term 5, and connecting the servo amp power supply to the outer most terminals, 9 and 15. Thanks for the help!

Now I need to deal with the +24VDC line, which is at +31V. I find this odd considering I have correct voltage at input to the relevant transformers, and the -22VDC line seems to be in spec at -22.3VDC. I attached a picture of the relevant wiring diagram. Probing between 12 and 13 for both transformers I measured 110VAC.

What is the tolerance on +24V components? I believe the only components I'll be running with 24V is the E-stop, limit and home switches. I assume 31V would be too high, but would 22V be too low?
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Last edit: 03 Aug 2018 18:34 by tightmopedman9.

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03 Aug 2018 19:35 #115544 by tommylight
31V in some cases is to much, in some it poses no problem. On the other hand, 22V will do just fine.

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07 Aug 2018 03:34 #115720 by tightmopedman9
Retrofitted the encoders today. Luckily it was an almost plug and play ordeal. I got E5 optical encoders from USDigital for a 10mm shaft, which matches the diameter on the upper end of the shaft on the equipped SEM MT30R4-33 servos. All I had to do was make a standoff of aluminum and re-pin the factory connector; both the factory encoder and the E5 share the same 2x5 .1" pin spacing. I retained the external factory connectors as well. I was able to bolt back on the factory encoder caps so it only took about 1hr to retrofit all 3.

I'm almost ready to start testing motion, I have all the encoders wired to the 7i77, and home and limit switches too. I need to figure out how to fix my 24V over voltage problem though. I'm not sure what the problem is as I haven't touched this part of the power supply. Voltage input is 110V, and spec in the manual is listed as 110-120V. Output sits at 31.4V and I don't feel comfortable running so close to the 7i77's limit of 32V. Since all I need to run is air solenoids for the lube system, mister and power for the limit/home switches, I assume I could get a 5A 24V power supply, but I'd rather fix what I have now in case the need for more 24V power arises.

Originally, the machine had contactors for the servos and the contactors would only be continuous when the axis drive was enabled. I'm not sure if an E-stop or limit switch opened the contactors. I removed the contactors to make things simpler, bad idea?

Regarding limit switches, should I put E-stop and axis limits on different inputs, does it matter? Right now they're all daisy chained to INPUT6.
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07 Aug 2018 03:37 #115721 by bevins
You took the tachs off and had enough shaft to mount the encoders?

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07 Aug 2018 15:46 #115754 by tightmopedman9
I retained the tachs, I want to have the option to tune the servos in velocity mode, which I will try first.

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10 Aug 2018 21:45 #115871 by tightmopedman9
I've got the encoders reading properly, and I was able to jog all the axis and make the machine move. Motion was surprisingly smoother than I had anticipated for the first test.

Now I've got a rather strange problem. Nothing happens when I open LinuxCNC config picker. I opened it earlier today without problem, and I've restarted the computer multiple times, but nothing seems to happen when I try and execute the program. I'm a total Linux noob, so I'm probably missing something rather dumb.

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