Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: Overloaded on April 09, 2008, 11:51:25 PM
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Greetings, :)
I found 2 of these in some recently purchased surplus lots.
I would like to know if I could use one of them with Mach on the knee of my bridgeport and what driver and power supply would be recommended.
Or are they too big ?
Thanks,
RC
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What proportion of these specs. would I expect to get by using a 65V-20A PS and a Gecko ?
Thanks,
RC
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You may get away with the Rutex 2020 to drive them but Geckos and Tek10s will be too small on both Volts and Current. The continuous current on the Rutex is well within these drives but the peak just states 200A for less than 1ms so not sure exatly how they would work out as your peak is a lot less than 220Amps being 65Amps but still may have to be carefull on the tuning.
I have been down this road with my Lathe, granted its motors were huge compared to that but I was just throwing bad money after bad, just wish I had moved onto the AC servos from eBay sooner LOL. At least I knew for the Mill and didnt have to go through all the expense of my magic smoke fun that I had with the lathe LOL
Hood
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Thanks Hood.
I'm not commited to using these. They were "thrown in" as part of a deal.
I have not seen a dc ps that even comes close. If I found one, I probably couldnt afford it !
?: There is an encoder on it and also 2 lighter gauge wires coming out of the case beside the heavy red and black motor wires.
I took the end plate off to investigate and found 4 very small brushes separate from the main motor brushes.
Could someone please explain......briefly ?
RC
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You can build a Power supply easily enough, transformer, capacitor and rectifier is all you need.
The brushes will be the Tach, not needed for Mach but other controlers need a tach to tell what the speed is. Also they may or may not be encoders, could be resolvers but even if they are encoders they may still not put out TTL, some put out a sine wave etc.
Hood
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You will see on the motor plate it has Tacho 7 V/KRPM, that means for every 1000RPM the motor is doing 7 volts will be produced, so by measuring the voltage the control knows the speed at any given point in time. As I said though its not needed with Mach so if you use the motors you can just remove the brushes.
Hood
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Thanks Hood,
Not sure how to go about determining the values for a toroidal and the other parts.
Would 120v 20a be adequate ? That's a VA rating of 2400 ?
I found a tutorial for stepper ps's which says the V should be motor V*20, but it looks like it is different for servos.
I'll get some info off of the enc/res to maybe determine what they are.
Good money after bad you say...........hmmmmm, I'm learning every day. (still not commited, just curious.....AC bound hopefully)
Thanks again for your help,
RC
This is from B. Campbells link:
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From CNC Teknix Tek10 User Manual
D2.1 Transformer Voltage Rating
The transformer should have a secondary output voltage 0.717 times lower than the DC voltage required
for the motors, ie. If your motors require 65VDC your transformer secondary voltage should be no more
than 65 * 0.717 or 46.6VAC.
D2.2 Transformer Current Rating
The current rating should be large enough to handle all motors running at full power simultaneously. If you
have a 3 axis system with each motor drawing a maximum average current of 10A, then the transformer
secondary should be capable of delivering at least 30A. Note that the servo driver has an adjustable peak
current limit. Average continuous current will be 20 to 60% below this value depending on your motor,
torque and acceleration setup. Conversion of AC to DC does lower this current, as it also raises the
voltage, but with a large filter capacitor it should still be sufficient. If in doubt it is better to get bigger rather
than smaller.
D2.3 Rectifier
Rectification can, in most cases, be a standard bridge rectifier, so long as the current rating is not
exceeded. If the total current draw is in excess of 25A then it is much better to make up a rectifier using
large stud diodes. If you do not have any experience in electronics then it is advisable to seek help in
making up this rectifier.
D2.4 Capacitance
The power supply needs enough capacitance to control the ripple voltage to under 2% at maximum load. A
capacitance (C1) value of this should be such that it provides at least 1,000uF (2,000uF recommended) of
capacity for every 1 Amp of current draw, so if your motors draw a total of 25A then you will need a
capacitance of at least 25,000uF. This can be one large capacitor or 2 or more smaller capacitors
connected in parallel. Mount the capacitance, power supply, as close to the drivers as possible.
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HOT DANG HOOD ! Just what I was looking for !
Now....can you tell from these pics if this is an encoder or a resolver ?
I almost guess it is a 500 count ? ? ?
Lets see......(help me fill in the blanks +/-, just a rough idea here)
Power supply (home made) $___
2 Rutex 2020's $570
2 - 1000 cnt enc's (if ness) $___
Thanks,
RC
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Encoders should be fine from a quick look at the pdf anyway, see here http://www.beiied.com/PDFs2/H20_Incremental_Encoder.pdf
Cant really help with the prices but I know it will be a lot less in the USA than it is in the UK :(
Hood
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Hey Hood,
That's all I need for now. They even have a pinout...cool.
I guess I'm ready for some of that "Magic Smoke Fun" you mentioned earlier.
Tell me about it.....I HATE SMOKE.
Thanks again,
RC 8)
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Hello...Me again,
What does the 11.3A represent on this motor plate ? Is that what I am to use to calculate the PS requirements ?
If so, what does the 65A represent ?
I doesn't look like the leads on this motor could handle 65A.
I am trying to determine what power supply I would need to run 2 of these with mach on a large homemade wood turning lathe. If volts is speed, 100v would be good enough for this app. But the amps....65*2 ? ? ? Can't be right, can it ?
The biggist toroid I can find is 1500w.
I can't find anything close !
RC
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The 11.3Amps is your continuous Amps , the 65Amps is you Max.
In theory you should have a powersupply that can deliver the max that each motor will demand but you will probably get away with less. Your 100v toroidal at 1.5KVA is only giving you 15Amps so its on the low side by quite a bit but there is nothing to stop you getting a few of them and connect in parallel. Your capacatance is going to need to be hefty as well but again you can connect in parallel to get up there.
Just thinking out loud here and there must be a reason why its a stupid thought but I cant think of it at the moment, apart from no isolation, so I will speak these thoughts:)
You guys in the USA have a mains of 110v do you not? What if you put the mains through a switch to a rectifier and then smoothed the rectifiers output. That way your mains would be your limiting factor for current. Your DC would be 1.41 higher than the mains so that would be just about perfect for your Max of the motor. There must be a reason this is not done, just seems too simple.
Hood
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Funny you brought that up...I was thinking the same thing but was afraid to ask about it.
I even looked for just a rectifier, found this but don't know exactly what it is.
Would it be OK to build 2 PS's ? one 1500w for each motor ?
Thanks Hood,
RC
Might just wait for AC.
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Not sure what that is and with no specs or model number there is not a lot to go on LOL Looks more like a small power supply to me rather than just a rectifier.
I still dont see a reason why mains wont do, hopefully someone will jump in and tell me what an idiot I am and that it cant be done for ***** reason.
Yes you could have seperate power supplies for each motor/drive, whether the 15Amps would be suffient, I dont think it would, I would be inclined to go 45Amps per supply. Obviously things are starting to get expensive with all these transformers, rectifiers and capacitors :(
Hood
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I see now what you mean. Maybe I should quit while I'm only out $30.00 for the 2 motors. :(
These should work though. :D
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Presume they are capacitors but what voltage/capacitance are they?
Hood
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They are labled Siemens capacitors. Not sure of the ratings. I didn't check.
I figure I'll just let this project die a peaceful death...before I run out of $ just to see smoke.
Thanks Hood,
RC