routercnc_MK3

[routercnc]

Thanks Geoffrey,

Starting to enjoy the electronics but would really like to finish it soon !

Can anyone confirm that using an SSR (25A) is OK to control the 2 power supplys? My plan is to apply 12V DC across the DC side and switch the 240V AC supply of the live cable to the 72V linear power supply primary, and also to the live cable of the 32V SMPS.


I understand that when SSRs are 'off' there is still a small voltage which passes through the AC side so in theory the drivers are still powered, although the voltage is very small. Is this the case and should I be concerned about it? Should I add anything else?

I also understand that an SSR works well with pure resistive loads - but I think the linear supply is a heavily inductive load with voltage and current out of phase. Is this the case and again is it a problem for these SSR devices?

I don't know what type of load the SMPS is but again will this switch well with the SSR?

See post #62 for the circuit diagram - the SSR is slightly right of centre.

This is a sketch of where it will be located (red rectangle):


Thanks for your help

[routercnc]

OK, I've added the 25A SSR but am not sure it is the right device to use to switch the linear supply. Here's why . . .

The SSR is connected to the e-stop circuit to cut or supply power to the driver power suppliers. To test it out I tried it on the driver supplies one at a time. When I just connected it to the SMPS (30V) it all worked fine (on the one time I tried it). But when I connected it to the linear power supply (750VA coil, 40,000uF caps, 72V output) the MCB tripped (6A type D). Previously on the couple of times I tried it without the SSR it did not trip.

I'm now convinced that the SSR is not the right switching device for linear supplies due to the high inductance of the load, but I'd welcome a second opinion. I've been hesitating using a contactor because they all seem to be 24V and my box runs 12V. But I now think it is the only way so I'll have to modify all the 12V items to work with 24V. I did look at 12V to 24V DC-DC convertors but didn't like the idea of running it for extended periods to hold the contactor closed. Plus, I think they give out electrical noise?

So to convert the box to 24V needs a resistor for the 12V LED, and either resistors for the mechanical relays, or most likely swap them out for 24V versions. The pump and lights are 12V each so I can add them in series and switch both at once (instead of independently).

So the big question is what current rating of contactor do I need to switch the big linear supply (X,A,Y axes) and the SMPS (Z axis)? I'm guessing many tens of amps at least? The inrush current on this linear supply is quite high I suspect but the online calculations for current spec seem very involved. Does anyone have an idea of what to use? I don't want to run it for a bit then burn it out.

Thanks

[njhussey]

I think I've got this one...http://chaloncomponents.co.uk/epages...ucts/NC1-1210Z but without looking at either it of the paperwork I can't be 100%. My PSU is a 625VA unit and also going through it is the 230V Nema 34 driver and 24V PSU.

I'm sure someone far more electrickery minded will pop along soon!

[routercnc]

Hi Neil

Thanks for that. Google search shows this is 12A which I think would be ok for continuous running just not sure about the inrush. Is yours powered up yet and running everything connected to it without problems? Thanks

[njhussey]

Unfortunately mine's had nothing done on it in the last 2 and a bit weeks as one of my colleagues (there's only 3 of us in the office) is on long term sick so I'm now doing all the design and engineering as well as all the other stuff I normally do so this has taken a backseat

I got the 12A one as I was going to put a soft start on my torroid....not got round to that yet. I'll probably do it if I have problems.....

[routercnc]

Hi Neil,

Sorry to hear that - it's so close to being finished.

On my machine I've re-drawn my circuit diagram to run the control side from 24V DC instead of 12V. I've ordered a 24V 5A SMPS and 2off 24V 4PDT DIN relays, laid out the 12V cooling pump and fan in series to give 24V load, and will drop a resistor (680ohm 1/2 Watt) onto the 12V LED line.


Those are the easy bits. But can anyone out there help with the following? I'm missing the contactor to switch on the 70V linear power supply and 30V SMPS for the 4 drivers. This will connect after the 6A type D MCB. I keep reading around on this and am getting no-where. There are 2 problems:

One is that I can't find a simple way to work out the inrush current on the power supply so don't know the peak current rating for the contactor.

Second is that contactors appear to be rated for different applications, labelled AC1, AC2,AC3 .. .AC6a, AC6b . . . For example AC3 is for motors, AC6a is for transformers etc. I can't seem to find any that are 24V DC coil with AC6a rating. All are AC3 rating which is really for motors?

I noticed Dean posted a drawing in Neil's build log (e-stop circuit) with a 25A contactor so that is my starting point. Is this an AC3 unit? If so does this work OK with a high inductive load such as the transformer?

All real world experiences and advice welcome as the Chint 25A (NC1-2510Z) AC3 24V DC coil is about £50 when you add delivery and VAT.
http://chaloncomponents.co.uk/epages...0Contactors%22

Finally is it best to isolate both the L and N as I've drawn? I assume I should leave the earth permanently connected to the devices being switched i.e. not run earth through the contactor?

Thanks

[routercnc]

Hi Dean - PM sent