routercnc_MK3

[routercnc]

Got the 24V relay and the contactor wired in earlier this week. But when I energise the 24V relay, the contactor switches but the MCB for the linear supply then trips out. Tried it twice and it tripped both times.
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Wiring diagram re-posted here:

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Here is a close up picture if it helps:

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The powering up sequence is:
1. Plug in and switch on at wall - this powers up the 24V PSU
2. Switch master on/off switch which puts the system into e-stop mode and lights up the red LED
3. Press the RESET momentary button which switches off the red LED
4. This energises the 24V master relay (which self-latches)
5. The master relay makes a circuit which runs 24V to the contactor A1/A2
6. The contactor switches on (with a click, and the lever indicator on the front moves to I)
7. This takes the mains power from the 6A type D MCB . . .
8. . . . and feeds it to the linear PSU (which is connected to 3 drives), but the MCB immediately trips
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If I disconnect the linear PSU then the relay, MCB and contactor operate and power up correctly and stay on so it would seem that the transformer inrush is too high for the MCB?
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Previously with the linear supply connected to one driver and just through the MCB without the contactor it has switched on (on the one and only time I tried it) without a problem.
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So, what to try? - What is the reason for most of the current draw ? -
Inrush through the 'shorted' coil until the magnetic field is established ? (750VA 2x24)
Charging up the capacitors (40,000uF) ?
Doing the above and powering up the 3off DQ860MA 80V drivers ?
Or some from each ?
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I could try switching on and off several times without any drive connected
I could then try disconnecting the AC supply to the rectifier and see if the MCB stays on with just the inrush through the coil - is that OK to do?
If that is OK I could unsolder one of the capacitors to reduce the charging draw.
Up-spec the MCB ?
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Any ideas? thanks

EDIT:
Bit of reading around and found a document from Allen Bradley, who make lots of good control gear. As I'm protecting the secondary with fuses I can go a bit higher on the primary protection as it is 'just' protecting the wire to the coil and the coil itself. So can probably go to 10A - my logic being:

10A type D should offer around 200A peak for a couple of cycles during switch on
During normal use I'm expecting a couple of amps, so will be OK there
If there is a problem on the primary the 10A MCB should go first as the coil can take 15A and the wall fuse is 13A
Chalon sell the double pole 10A type D for £10.25 all in . . !
Worth a try?

[JAZZCNC]

EDIT:
Bit of reading around and found a document from Allen Bradley, who make lots of good control gear. As I'm protecting the secondary with fuses I can go a bit higher on the primary protection as it is 'just' protecting the wire to the coil and the coil itself. So can probably go to 10A - my logic being:

10A type D should offer around 200A peak for a couple of cycles during switch on
During normal use I'm expecting a couple of amps, so will be OK there
If there is a problem on the primary the 10A MCB should go first as the coil can take 15A and the wall fuse is 13A
Chalon sell the double pole 10A type D for £10.25 all in . . !
Worth a try?

Exactly What I was going to suggest. I think you'll find that you can even get away with 10A Type C. It's worked for me many times before just to get going so try this if you have one.!

[Boyan Silyavski]

Now if you make a soft start for the PSU and i will officially say you are the master of enclosures


http://www.ebay.co.uk/itm/220V-Class...item3f3f435e81

http://electronics-diy.com/soft-star...wer-supply.php

[routercnc]

Silyavski
Wow, wouldn't say I'm the master of enclosures - I'm making most of it up as I go along!

Looked at soft start options but I only found home made circuits so thanks for those links. Hope to get away without them but good to know there is a ready made module should I need it

[routercnc]

Good news !

10A MCB type D arrived today so I swapped out the 6A unit, held my breath, and switched it on. The contactor clicked and the drivers powered up !
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Could have been lucky (by chanced switched at maximum peak voltage) so tried it again. Same thing, worked fine. Switched off and tried one more time. All fine again. All this was with 3 drivers connected (but no motors yet).
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Switched off again and checked the decay time on the linear supply and it dropped from 72V at just over 1V per second, and stopped at around 3V.
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Here is the proof:

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And here is the new unit (the one on the right):

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It will be the weekend at the earliest now but hope to mount it on the wall and plug in all the cables etc. to get the basic machine running. It might be the following weekend but hope to machine out the control panel that I was cutting out when it went bang last time.
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Purely for neatness a few days ago I ordered another DQ860MA 80V stepper driver for the Z axis. When it arrives this means all 4 drivers can run from the single linear supply (I sized it at 750VA to cope), and I can get rid of the 32V SMPS in the top corner. The Z axis stepper is 1.8Nm and only around 1.7mH so I think I need to wire it in series to keep the current down.
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I also ordered a small 5V SMPS so I don't need to take a feed from the PC molex power supply. Just feels better this way. The top of the control box will then be shuffled around a bit to get a really nice layout and it will allow me to seperate the power and signals even more than current.

[JAZZCNC]

Coming along nice Barry hopefully no more troubles.!

[routercnc]

I thought I wait for decent progress before posting again.

Finally mounted it to the wall and wired in the stepper motors. At 72V it jogs around much faster than the previous machine!


The monitor will mount to the door, probably on a small pivoting bracket.

I've swapped out the Z axis stepper driver to another DQ860MA and am running it off the main linear power supply. This meant I could remove the 34V SMPS power supply. I've also added a 5V PSU to run the breakout board (next to the invertor).


I decided after much thought to put both X axis stepper drivers on the same fuse and up the rating to 10A (Y and Z are on 5A each). I was worried that if one fuse blew the gantry would quickly twist and do some damage. This way if one goes they both stop. What has everyone else done?


Recently I managed to machine the front panel and offer it up as a trial. Fits OK but was a pain to machine. It is 3mm aluminium 1050 grade which is very soft. Didn't help that I'd not paid much attention to the 6mm bit I ordered recently and it arrived with 3 flutes. In the end I had to machine it very slowly (120mm/min at 1mm DOC) otherwise it stuck to the cutter.


It should look like this when finished:


Still need to wiring up all the buttons to the panel, add the POKEYs board to the back, wire in the external e-stop, the machine limits and proximity home switches . . . . .

Can't come soon enough to be honest as I managed to jog the machine into the (non-functioning) micro-switches on the X axis and smash them to pieces, plus bend the end stops a bit. Those motors have some power now on 72V !

Another problem is this afternoon the PC just switched off without warning (wasn't cutting just doing a bit of CAM). When I switched it on it said there was a keyboard error and would not start !! More to sort out - but it will have to wait for my next session.

[routercnc]

Thanks Dean
OK will get my order in with Chalon . . .