Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: alcwell on February 07, 2012, 04:46:02 PM
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Having done some research what I am planning to do is:-
Keep the SEM servo motors replacing the encoders with AMT103 encoders from Digikey
Replace the servo drives with CNCDrive DG2S-16035, which I believe replaced the Dugong models
http://www.cncdrive.com/DG2S_16035.html (http://www.cncdrive.com/DG2S_16035.html)
I am not sure what to do about powering the drives or exactly how large a power supply is required to get reasonable performance. Previously I have built my own power supplies but, these were for smaller machines with stepper motors so voltage and current requirements were less. The plate on the motors says 140V and the datasheet that I found lists continuous stall current at 6.1A. I would also like to run the machine from 230V single phase.
I have done some searching and found details of a few conversions but a lot of these used Gecko drives and limited the power supply to 80V.
Can anyone make any suggestions or point me in the direction of some info?
Thanks
Alastair
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Do you not have the original power supply? If you do that would give you a starting point for the volatge and it should also have rectifiers and caps which you could reuse even if it was 3 phase.
Hood
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That was quick Hood. I wasn't expecting anything until at least tomorrow!
The original transformer outputs 180V before rectification from a 415V supply. From my understanding the original drives (Bosch ZX15-1-240V) rectify and reduce the voltage to that required by the motors.
I had hoped to use the existing transformer, for testing at least. There are multiple input and output taps so I hoped to get a combination that would give a useable output voltage from a 240V input. What I am not sure of is the effect on the transformer of using a combination of input and output taps that are out of spec, so to speak.
Thanks
Alastair
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Would have to be careful if you were thinking of connecting single phase into a three phase transformer I would imagine. Depends on the makeup of the transformer and whether you can separate it out into 3 individual transformers so to speak.
Hood
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It only uses two of the three phases so I think that it should work from single phase. However, I would appreciate of anyone could give some advice in advance of the effects of this and operating at an input and output voltage combination that it may not have been designed for.
Thanks
Alastair
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Ah ok then that should be fine, are you UK or USA or? Just wondering what your mains are, ie UK 240v Live and a Neutral where USA can be 2 110v lives I think.
Hood
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In UK
Alastair
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Ok then if its just a two phase tranformer then putting 240v and neutral to the inputs you should get around 104v output then when rectified and smoothed you would have about 180v which would be too high for you so you would have to see what secondary tappings you have.
As far as I am aware transformers are rated VA so shouldnt be a problem using 240 instead of 415, dont suppose you know what the rating is in VA/KVA?.
Hood
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I don't know the VA rating of the transformer at the moment as it is not marked on the drawings. I will look to see if it is marked on the transformer the next time I am at the machine.
Wouldn't 104VAC be approx. 145VDC when rectified / smoothed? Or have i got my rules of thumb wrong!!
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Sorry you have it right, was getting mixed up with three phase, well it was late ;D
If the transformer was good enough for the drives that were in then I would say it has to be good enough for the new drives so probably not worth worrying about the KVA.
Hood
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Thanks for the help Hood.
I will try the original transformer and see how it goes while setting up and testing.
If it works well all is good, if not I can come back to it.
Thanks
Alastair
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You will likely need more capacitance than the original had, maybe not, but the few I have seen have less than the 1000-2000uF per amp that seems to be standard to keep ripple low.
Hood
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Yes it will definitely need some capacitance added as there currently isn’t any! Or at least none that is external to the drives.
The 180VAC from the transformer is fed directly to the drives, each drive also has an external choke coil.
Alastair
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Ah ok, thats the best way if the drives handle it but sadly none of the type normally used with Mach do. The AC servo drives I use take mains right in but suppose thats why there is a big difference in prices, well one of the reasons.
Hood