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Proteus
20-10-2016, 07:22 PM
I have 1 x 230Vac/2x60Vdc-12,5Adc toroidal lineary power supplie, but i`m considering bying one more and an alternative installation.
They are to be used in my VMC300 mill conversion with 3 pcs NEMA34 640 oz-in 4.5A Stepper Motor, 1 pcs NEMA23 282oz-in 3.0A and 4 pcs Leadshine AM882 drivers.
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Frankly, i`m not sure 1 PSU is enough. Datasheet says 58,2V at 0 load, 47,9V at 21 Amps/1,7Vrms ripple.
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Can i install 2 of these in parallell (Both output in parallell after each rectifier bridge/capacitors)?
Or would it be a better solution to install them in parallell with a common(shared) rectfier brigde and capacitors?
The PSU is equipped with 2 pcs 10000uF/80V capacitors, vs my old 85V PSU which is equipped with dual 33000uF/63V capacitors.
Using all 4 capacitors would increase capacity, but might not be a good idea...
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Any hot advice gents ?

Clive S
20-10-2016, 07:48 PM
my old 85V PSU which is equipped with dual 33000uF/63V You will have trouble with these caps as they are not rated high enough you will need a min of 100V caps and probably a bit higher.

Proteus
20-10-2016, 07:59 PM
You will have trouble with these caps as they are not rated high enough you will need a min of 100V caps and probably a bit higher.

i know, and i have already found some 100V Epcos Aluminium Electrolytic Capacitors on RS-Online with screw terminals.
But that`s why i mentioned my old 85V PSU equipped with 63V capacitors :thumbdown:

JAZZCNC
20-10-2016, 07:59 PM
Not sure what your meaning.? If they have 2 x 60Vdc outputs why would you rectifie them.? Do you mean 2 x 60Vac.?

If so then you'll still have trouble because the voltage after being rectified will be too high for the AM882.

Proteus
20-10-2016, 08:15 PM
Not sure what your meaning.? If they have 2 x 60Vdc outputs why would you rectifie them.? Do you mean 2 x 60Vac.?
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No, they have an output(rectified) of 60Vdc(58,2Vdc), and 40Vac before the rectifiers.
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If so then you'll still have trouble because the voltage after being rectified will be too high for the AM882.
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The AM882 can withstand 80Vdc With a typical supply voltage of 68Vdc.

Proteus
20-10-2016, 08:18 PM
By the way, why does everyone advice lineary PSU instead of high quality switching rectifier PSU`s ?

Proteus
20-10-2016, 08:35 PM
By the way, why does everyone advice lineary PSU instead of high quality switching rectifier PSU`s ?

I got my hands on a high quality Eltek Flatpack2 2KW adjustable 53,5 to 67Vdc handling 30 Amps at 65Vdc, Ripple=150mV PP/2mV psophometric.
Hmmm... Can`t see any reason not to use that one..

JAZZCNC
20-10-2016, 08:54 PM
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The AM882 can withstand 80Vdc With a typical supply voltage of 68Vdc.

Yes After fitting a few hundred I know this and exactly why I posted. 60Vac after being recitied will give aprox 83Vdc which will release the magic smoke.!!

Edit: Ok I see you replied with No 60vdc but was included in my Quote so didn't see. Thou Still doesn't explain why you mentioned Rectifying.?

Proteus
20-10-2016, 10:22 PM
Yes After fitting a few hundred I know this and exactly why I posted. 60Vac after being recitied will give aprox 83Vdc which will release the magic smoke.!!

Edit: Ok I see you replied with No 60vdc but was included in my Quote so didn't see. Thou Still doesn't explain why you mentioned Rectifying.?
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I was suggesting having 2 PSU Connected in parallell after the rectifier bridge. However that is not the best idea, but maybe better than having both 40Vac outputs Connected to 1 bridge.
But what do you think about using a high quality switched PSU With the specs i mentioned Dean ?

m_c
20-10-2016, 11:22 PM
I got my hands on a high quality Eltek Flatpack2 2KW adjustable 53,5 to 67Vdc handling 30 Amps at 65Vdc, Ripple=150mV PP/2mV psophometric.
Hmmm... Can`t see any reason not to use that one..

Mostly because when decelerating hard, stepper drives dump power back into the power supply.
With a linear supply it (more specifically the capacitor) will absorb the current and it will cause a slight power rise until things stop decelerating, and provided things have enough headroom voltage wise, it won't be an issue.
Whereas with a SMPS, they don't have a big capacitor, so the same deceleration can cause a noticeable power spike. Depending on the SMPS, it may shut down, go into fault, or simply go pop, but the same voltage spike can quite easily cause the stepper drives to go overvoltage and release the magic smoke.
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Off course, you can avoid the issue by implementing reverse current dumps (the gecko drive website used to have a schematic for one), but it's added things to go wrong.

JAZZCNC
20-10-2016, 11:28 PM
.But what do you think about using a high quality switched PSU With the specs i mentioned Dean ?

Thanks Moray saved me some typing. .:encouragement: . . . . . . Nothing else to add to what M_C said.