Leadshine Mx3660 shunt regulator query

[the great waldo]

Hello All
I've just taken the plunge and bought a Leadshine MX3660 all in one box. The manual recommends using a shunt regulator/ capacitor to stop back voltage? blowing up the stepper drivers in an e stop situation. Does anyone know of the values of the capacitor required (48 volt switching power supply 3 x Nanotec ST6018L3008-A 4.3V 3.0amp stepper wired in parallel ) Or does any one have a circuit diagram of a shunt regulator that I could make. Also would it be better to use a non switching power supply transformer caps and rectifier ?
Thanks in advance

Cheers

Andrew

[JAZZCNC]

Also would it be better to use a non switching power supply transformer caps and rectifier ?
Thanks in advance

Yes this is what you require. Switching PSU isn't recommended for CNC because the back EMF from steppers can cause you trouble with PSU protection shutting the unit down.
Toroidal transformer with caps & Rectifier is what you require for best operation.

[the great waldo]

Hi Jazz

Thanks for the reply. I read somewhere that a 4700uf Cap should be put across the + - volt out from supply. Would that be needed as well as with a non switching power supply or could that be part of the smoothing circuit in the psu maybe upping the values of the Capacitors. It's been years since I did much electronics stuff mainly audio projects from everyday electronics and electronics today mags !!

Cheers

Andrew

[JAZZCNC]

Capacitors are the smoothing/shunt circuit and the PSU output you require will determine the Capacitance required.
I think the MX3660 uses 60Vdc drives so you'll not want much more than 50V output and if using 4A motors you'll require aprox 8A output for 3 x motors(65% total amps).
So Transformer with 2 x 18Vac secondarys wired in series and 300Va will give you aprox 50V with 8.3A or if require more amps go with 500Va for just under 14A.
With 300Va you'll get away with 2 x 4700uf-80 or 100V Caps wired in parallel but for the little extra they cost I'd go with 3 x 4700uf to give that bit more smoothing.

25A or 35A Rectifier.

[the great waldo]

Hi Jazz

Thanks very much for the info. I had just checked out this transformer http://www.trafoshop24.de/rk-transformatoren-500-va/84-ringkerntransformator-500va-2x18v-rk-ec500.html Is there any benefit from using toroidial as opposed to the old square transformers from back in the day ?

Cheers
Andrew

[Doddy]

Hi Jazz

Thanks very much for the info. I had just checked out this transformer http://www.trafoshop24.de/rk-transformatoren-500-va/84-ringkerntransformator-500va-2x18v-rk-ec500.html Is there any benefit from using toroidial as opposed to the old square transformers from back in the day ?

Cheers
Andrew

Advantages of toroidal transformers is pretty much weight, efficiency, reduced em field and, typically, cost. They come with a bit of a disadvantage of high-inrush current, but that can either be ignored or designed-out.

[Gary]

Leadshine makes a shunt regulator specificaly for this.
https://www.zappautomation.co.uk/sr50w-shunt-regulator.html

You can use a switching supply with a stepper system, but they are not ideal, but if you do, use a nonregulated switching supply. like the sps type.


Hello All
I've just taken the plunge and bought a Leadshine MX3660 all in one box. The manual recommends using a shunt regulator/ capacitor to stop back voltage? blowing up the stepper drivers in an e stop situation. Does anyone know of the values of the capacitor required (48 volt switching power supply 3 x Nanotec ST6018L3008-A 4.3V 3.0amp stepper wired in parallel ) Or does any one have a circuit diagram of a shunt regulator that I could make. Also would it be better to use a non switching power supply transformer caps and rectifier ?
Thanks in advance

Cheers

Andrew

[the great waldo]

Thank you Gary
I'll be going with a nonregulated supply. Just out of interest what is an sps type ?

Cheers

Andrew

[Gary]

Like this.
https://www.zappautomation.co.uk/sps487-unregulated-switching-power-supply.html


Thank you Gary
I'll be going with a nonregulated supply. Just out of interest what is an sps type ?

Cheers

Andrew

[the great waldo]

Hi Gary.
Thank you.
Andrew

[the great waldo]

Two last questions on my power supply project. Is it worth putting an inrush current limiter http://www.produktinfo.conrad.com/datenblaetter/1200000-1299999/001297741-da-01-en-EINSCHALTSTROMBEGRENZER_SESB_250V_16A.pdf in with the power supply. The transformer will be 500va 2x18v 35amp 600v bridge rectifier 3 x 4700uf 100v caps. Is a heat sink needed for the rectifier or is it enough to bolt the rectifier to the metal case ?

Cheers in advance

Andrew

[Doddy]

Two last questions on my power supply project. Is it worth putting an inrush current limiter http://www.produktinfo.conrad.com/datenblaetter/1200000-1299999/001297741-da-01-en-EINSCHALTSTROMBEGRENZER_SESB_250V_16A.pdf in with the power supply.


Your call. Personally I've used an NTC 10D-15 thermistor in series with the transformer primary (mine is an 800VA toroidal transformer). I've not put the PSU under significant load (yet!) but it's working fine. If I have problems with the NTC heating then I can replace at a later date with a similar limiter to what you linked, or place a relay across it. But I'm going to test it before spending £40.


The transformer will be 500va 2x18v 35amp 600v bridge rectifier 3 x 4700uf 100v caps. Is a heat sink needed for the rectifier or is it enough to bolt the rectifier to the metal case ?


You need the data sheet for the rectifier to answer that one. And your case size

I'm going to use some wet-fingered maths. Say you're dropping 1V across each diode element in the rectifier at full load, and two diodes in conduction at any time, so you're dropping 2V (out of 36) at a full-load current of (500/36) about 14A. That's 2x14 (=28, let's call it 30) watts dissipated in the bridge. Use https://www.heatsinkcalculator.com/free-resources/flat-plate-heat-sink-calculator.html - you may need to guess at some of the numbers. Using 1.2mm mild steel and a 100mm x 100mm plate, that gives a junction temperature of 450 degrees C. You're aiming for a junction temperature below 150 degrees (better below 100 degrees). So - a 1.2mm 100x100 plate is clearly insufficient under full load. But you need to run the numbers for your enclosure. Based on a wet-finger keep-it-below-100-with-25-C-ambient, i.e. 75 degrees head-room, you need a thermal resistance of 75/30 = 2.5 degrees/Watt, which is no small heatsink.

One question. Why 2x18V secondaries in series?, why not 2x36V secondaries with independent rectifiers and smoothing capacitors. That way the thermal load through e.g. the BR is halved, for the cost of essentially 1 additional BR. Copper losses in the transformer and wiring are reduced. Use one half to drive 2 motors, the other half to drive the other motor (plus growth for a fourth). Common the 0V lines if you want.

[the great waldo]

Hi Doddy

I'll be wiring the transformer for 36 volts, I hadn't thought about the upgrade to a 4th axis. I'll use a heatsink (they aren't so expensive and fix it to the case ) I'll have a look at the thermistor. I'll be using a couple of fans in the case for good cooling. My old control box has a switching power supply and for some reason the inbuilt fan in the power supply really gets on my nerves with the noise it makes.

Cheers

Andrew

[the great waldo]

Hello Doddy
Hmmm!!

Youv'e got me thinking about the 2x36 transformers. Do you think 2x 4700uf on each output would be enough. The Mx3660 has a wiring diagram to connect a 4th stepper. The question is would I ever need it and or would I be forever building new control boxes to upgrade. It's a holiday here in Austria which gives me some time to check this out. I'm definitely warming to the 2x36 v transformer excuse the pun.
Cheers

Andrew

[Doddy]

Hello Doddy
Hmmm!!

Youv'e got me thinking about the 2x36 transformers. Do you think 2x 4700uf on each output would be enough. The Mx3660 has a wiring diagram to connect a 4th stepper. The question is would I ever need it and or would I be forever building new control boxes to upgrade. It's a holiday here in Austria which gives me some time to check this out. I'm definitely warming to the 2x36 v transformer excuse the pun.
Cheers

Andrew

Do I think?, put it this way - I've used 10,000uF on each of my 2x50V supplies - 2x4700uF is pretty much the same, so I think the answer is a yes.

[the great waldo]

Well that's a fairly clear answer. Thanks for your help.

Cheers
Andrew

[the great waldo]

Hi Doddy

I was having a beer last night and a thought came to me that I can't use the double rectifier supply as the mx3660 has only one power supply input connector. I should have noticed that before.

Cheers

Andrew

[Doddy]

Hi Doddy

I was having a beer last night and a thought came to me that I can't use the double rectifier supply as the mx3660 has only one power supply input connector. I should have noticed that before.

Cheers

Andrew

Aha, an all-in-one?, yup, fair cop.