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Author Topic: Can two 36v power supplies be used in series to get 72v?  (Read 31303 times)

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Offline simpson36

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Can two 36v power supplies be used in series to get 72v?
« on: April 14, 2009, 10:16:32 AM »
I'm using a 36v power supply which is  fine for the axis steppers, but I'm contemplating getting a 72v servo motor as well.

Q: can a pair of unregulated CNC power supplies (mine is from Keling) have thier outputs wired in series to get 72v or would that cause a problem?

Alternately, could a step up transformer be used to create the 72v for a single motor while the rest of the setup continued to run on 36v?

These are probably very rudimentary questions, but I'm not good with electrons so I appreciate the opinions and advice from those who are.

Thanks.
Re: Can two 36v power supplies be used in series to get 72v?
« Reply #1 on: April 14, 2009, 10:44:15 AM »
Connecting two supplies in series should work fine.

Regards,
Ray L.
Regards,
Ray L.
Re: Can two 36v power supplies be used in series to get 72v?
« Reply #2 on: April 14, 2009, 12:43:12 PM »
Some will work and some will not, you'll have to verify the spec of your power supply. Look for a PDF file from keling.

You can't use a step up transformer to crank up voltage from a DC source, you're looking for disaster, transformer only work for AC voltage
Re: Can two 36v power supplies be used in series to get 72v?
« Reply #3 on: April 14, 2009, 03:41:24 PM »
Some will work and some will not, you'll have to verify the spec of your power supply. Look for a PDF file from keling.

You can't use a step up transformer to crank up voltage from a DC source, you're looking for disaster, transformer only work for AC voltage

These are unregulated supplies - transformer, rectifier, filter caps.  There's no way it won't work....

Regards,
Ray L.
Regards,
Ray L.

Offline simpson36

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Re: Can two 36v power supplies be used in series to get 72v?
« Reply #4 on: April 15, 2009, 09:06:39 AM »
Thanks for the replies.

The power supply: (KL-320-36 36V/8.8 or 9.6A) http://www.kelinginc.net/SwitchingPowerSupply.html

 . . have 3 sets of terminals, but internally they are all connected together, so it is actually only one output from one rectifier/transformer. There are three caps, but again they are in parrallel and connected to the same trace on the output.

So, refining the question a bit; using two of these powere supplies, can I use a 36v terminal from each power supply to drive steppers @ 36v  and then also series wire a set of terminals to get the 72v for the servo motor?
Re: Can two 36v power supplies be used in series to get 72v?
« Reply #5 on: April 15, 2009, 11:06:31 AM »
Thanks for the replies.

The power supply: (KL-320-36 36V/8.8 or 9.6A) http://www.kelinginc.net/SwitchingPowerSupply.html

 . . have 3 sets of terminals, but internally they are all connected together, so it is actually only one output from one rectifier/transformer. There are three caps, but again they are in parrallel and connected to the same trace on the output.

So, refining the question a bit; using two of these powere supplies, can I use a 36v terminal from each power supply to drive steppers @ 36v  and then also series wire a set of terminals to get the 72v for the servo motor?

Yes.  Wire the - side of one to the + side of the other.  For a 36V device, you can use the two terminals from either supply, and for a 72V device use the unconnected + and - terminals.  It would be best if you used the "low" side 36V supply for the 36V devices (the one whose + terminal is connected to the - terminal of the other supply), so both 36V and 72V devices have the same "ground" reference.  Otherwise, you'll need to be VERY aware of which devices are using which "ground" reference, to avoid shorts.  And make sure the - side of the "high" side supply is NOT tied through its case to your system ground.

Regards,
Ray L.
Regards,
Ray L.

Offline Jeff_Birt

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Re: Can two 36v power supplies be used in series to get 72v?
« Reply #6 on: April 15, 2009, 12:25:46 PM »
Be VERY VERY careful. Unless the power supply is designed for series operation you will have problems. Many switch type power supplies tie the DC common to earth ground through a small resistor. Chaining two in series would be a bad idea. If a power supply can be put in series it will be stated so on the data sheet.
Happy machining , Jeff Birt
 

Offline simpson36

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Re: Can two 36v power supplies be used in series to get 72v?
« Reply #7 on: April 15, 2009, 12:37:23 PM »
THANKS guys!

This is exactly the sort of caveats I was looking for.

A wise man once said it is more important to know what you don't know than what you do know. I'm not good with electrons, so I appreciate the help.

I am capable of checking the items cautioned about. I am using a separate power supply for the electronics side of things and the Keling 36v goes only to the Gecko 203V drives, which are 'unkillable' per Gecko, so hopefully I can't do too much damage if I go ahead with this scheme.

However, I'm thinking it might be wise for me to buy the Gecko 320 and a little NEMA23 36v servo motor to play with first. I have the stepper thing pretty well figured out, but this will be my first taste of servos. Objective is to get some experience under my belt doing a usefull project (repowering my stepper driven indexer) before I do my next mill conversion . .  which will be 100% servo powered.

Thanks for the advice, much appreciated.
Re: Can two 36v power supplies be used in series to get 72v?
« Reply #8 on: April 15, 2009, 12:54:06 PM »
Some will work and some will not, you'll have to verify the spec of your power supply. Look for a PDF file from keling.


That's what I said.

Connecting two switching power supply in series or parallel if they are not designed for that purpose can be a bad thing and you're looking for trouble

Look at the Doc file attached



« Last Edit: April 15, 2009, 12:56:43 PM by ostie01 »
Re: Can two 36v power supplies be used in series to get 72v?
« Reply #9 on: April 15, 2009, 02:30:07 PM »
Be VERY VERY careful. Unless the power supply is designed for series operation you will have problems. Many switch type power supplies tie the DC common to earth ground through a small resistor. Chaining two in series would be a bad idea. If a power supply can be put in series it will be stated so on the data sheet.

It's ***NOT*** a switching power supply! It's a plain, unregulated linear supply!  There is absolutely no risk of damage.

Regards,
Ray L.
Regards,
Ray L.