A MYSTERY? 24VDC blowing fuses

[damunk]

As the title suggests; I have a fuse that is blowing on a 24VDC circuit.

I was worried I had damaged the servo motors as they cost a bomb.

the motors, I connect and disconnect at the BNC point on the diagram.

I plugged them in and it was blowing fuses. I tried 1a 2a 4a (4 amp is ample).

I thought it was a motor that was blown and causing a surge. I then swapped them over left and right and they both work.
I then realised I had plugged them the wrong way around but there should not be a wrong way around.

I just dont get it. Is it something to do with the negative rail on the 24VDC transformer? That I have wired the neutrals seperate.

The transformer is CP10.241 | PULS DIMENSION DIN Rail Power Supply, 100 → 240V ac ac Input, 24V dc dc Output, 10A Output, 240W | RS - https://uk.rs-online.com/web/p/din-rail-power-supplies/9159741?cm_mmc=UK-PLA-DS3A-_-bing-_-PLA_UK_EN_Catch+All-_-Electronic+Components,+Power+%26+Connectors-_-9159741&matchtype=e&pla-4574724306713135&cq_src=google_ads&cq_cmp=554644865&cq_term=&cq_plac=&cq_net=o&cq_plt=gp&gclid=9c35c57b04ee155e2fbca2c768090c1f&gclsrc=3p.ds&msclkid=9c35c57b04ee155e2fbca2c768090c1f



PULSE 24VDC 10A PSU; a pretty decent one.

 

[Avo Mk8]

I can't immediately see anything wrong, but you haven't mentioned the characteristics of the motors.
I'm curious about the use of BNC connectors for the power - are you using 2-pin ones with the current going through the pins, or just coaxial ones with current passing through the body?
Are your BNC's rated for several amps, as I was under the impression that 1 or 2 amps is normally their max current?
You could put a separate fuse in each motor supply, which might narrow down the problem if it happens again!
Finally how did you arrive at the conclusion that a 4A fuse is ample? You've got a beefy supply capable of delivering twice that - do you know what a motor takes off and on load?

Sorry for all the questions !

 

[mainline]

As above, Bnc type plugs are meant for RF and not for any substantial current.

Are you using coax for the terminations ?

 

[damunk]

I can't immediately see anything wrong, but you haven't mentioned the characteristics of the motors.
I'm curious about the use of BNC connectors for the power - are you using 2-pin ones with the current going through the pins, or just coaxial ones with current passing through the body?
Are your BNC's rated for several amps, as I was under the impression that 1 or 2 amps is normally their max current?
You could put a separate fuse in each motor supply, which might narrow down the problem if it happens again!
Finally how did you arrive at the conclusion that a 4A fuse is ample? You've got a beefy supply capable of delivering twice that - do you know what a motor takes off and on load?

Sorry for all the questions !

James; The connectors are indeed the 2 pin and I have wired the kill switch wire to the -24VDC .
Perhaps I wired one of them to -24VDC and the other to +24VDC on the second connector.
Not sure why it would mean it would work a certain way.

https://m.media-amazon.com/images/I/51MmOgnljOL._AC_UF1000,1000_QL80_.jpg

The GX12-2PIN are rated for 5 amps.

Wiring is 1.5mm2 so thats okay.

Each motor probably draws 1 to 1.5A if that.

I like the idea of a separate fuse.

 

[DPG]

Ah, those aren't BNC connectors, they are industrial connectors which are suitable for the job.

As above, BNC connectors are for RF (and also audio, test equipment etc.) use and are used with shielded coax cable.

 

[Avo Mk8]

James; The connectors are indeed the 2 pin and I have wired the kill switch wire to the -24VDC .
Perhaps I wired one of them to -24VDC and the other to +24VDC on the second connector.
Not sure why it would mean it would work a certain way.

https://m.media-amazon.com/images/I/51MmOgnljOL._AC_UF1000,1000_QL80_.jpg

The GX12-2PIN are rated for 5 amps.

Wiring is 1.5mm2 so thats okay.

Each motor probably draws 1 to 1.5A if that.

I like the idea of a separate fuse.

Thanks for the info. You'll be OK with those connectors then.

If your fuse blowing persists, there surely must be something up with the wiring. You haven't got one set of connectors (both plug and socket) wired the opposite way round to the other?