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Drive/Power supply Questions
« on: April 09, 2008, 11:51:25 PM »
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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« Last Edit: April 10, 2008, 06:36:24 AM by Overloaded »

Offline Hood

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Re: Drive/Power supply Questions
« Reply #1 on: April 10, 2008, 04:27:42 PM »
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
« Last Edit: April 10, 2008, 04:29:21 PM by Hood »
Re: Drive/Power supply Questions
« Reply #2 on: April 10, 2008, 07:15:22 PM »
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

Offline Hood

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Re: Drive/Power supply Questions
« Reply #3 on: April 10, 2008, 07:42:22 PM »
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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Re: Drive/Power supply Questions
« Reply #4 on: April 10, 2008, 07:58:06 PM »
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
Re: Drive/Power supply Questions
« Reply #5 on: April 11, 2008, 08:47:39 AM »
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:
« Last Edit: April 11, 2008, 09:09:14 AM by Overloaded »

Offline Hood

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Re: Drive/Power supply Questions
« Reply #6 on: April 11, 2008, 11:15:33 AM »
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.
Re: Drive/Power supply Questions
« Reply #7 on: April 11, 2008, 01:24:58 PM »
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

Offline Hood

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Re: Drive/Power supply Questions
« Reply #8 on: April 11, 2008, 01:34:17 PM »
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
Re: Drive/Power supply Questions
« Reply #9 on: April 11, 2008, 01:49:55 PM »
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)

 
« Last Edit: April 11, 2008, 03:37:45 PM by Overloaded »