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 ?