fuses not doing their job

Use a faster sweep through (fast-blo) fuse, try the same current rating first.
If you go too light, you could get nuisance blowing.
M.

 

More specifics needed. What gate motor and PSU, and were they meant to be mated together for this application?

What is "blow the power supply as well as...", what exactly failed at the discrete component level?

If the motor blows the PSU, wouldn't you need the motor replaced or choose a different PSU, not restart with the same combination that fails again and again? If you're repeatedly paying for the repair, you should insist on some warranty in writing to make them accountable for a bad result.

A fuse blows when there is already a fault, you should alleviate if not completely eliminate the failure point rather than just fuse it differently. Perhaps a better mated fuse is eventually a good idea but it's not the primary problem.

If you put in a perfectly sized fuse, it works, then the fault, fuse blows... if you put in a new fuse it'll just blow again, you still need to fix the fault.

 

Take the number of the fuse you are using and use the same current value, but fast blow, there are also very fast fuses aimed particularly at electronics, called rectifier fuses, these have a very fast sweep through so as to save the subsequent equipment in times of a surge, electrical storm etc.
You maybe getting over-voltage surges where you are.
How is the power managed in S. Africa?
What is the nature of the motor, BTW?
M.

 

I would also take a reading of the actual power consumed and fuse accordingly, often equip. manuf. over fuse.
The standard here in N.A. is generally 1.5x actual peak running current.
M.

 

If you are stating the only reason you're having problems is power line surges, then you need a surge protection circuit. A fuse alone will not prevent a damaging level of voltage getting through to the PSU.

However if your power is that bad you may need whole site surge protection. If you are not observing other equipment failures I would wonder if the PSU is simply low quality and cannot withstand high ambient temperatures.

Since you did not link to the PSU I assume no specs are available and it's just want gets bundled with that motor. If all the PSU needs to do is output a fair margin over 3A @ 12VDC, you shouldn't have much trouble finding a different PSU with a more robust design. Perhaps it needs to be rated WELL above 3A for extra thermal margin, so you can stuff it in a NEMA rated weatherproof housing if the location requires it.

I would not keep paying someone to repair something that keeps failing. Find a different option or insist on a warranty. IMO a different option is superior, warranty work can tend to get done at a snail's pace.

 

The OP did mention trying a surge limiter device.
I would be inclined to agree with @Minder , with a fast blow fuse. You may depend on the location that ‘any’ fuse has been fitted. That said, the OP needs to find the original fuse rating and type.
This is for an electric gate? I think. So a fast blow fuse is unsuitable due to excess current on power up. But a good idea for initial testing.

Martin

 

"How is the power managed in S. Africa?"
Ask any South African here that question and he'll be taken to hospital having bust a gut laughing

 

I don't agree that fast acting fuses will not protect surges.
Years ago with the popularity of 3ph SCR bridge circuit to drive large spindle and servo motors, these were used across the line and all had rectifier (ultra-fast) fuses, in the event of electrical storms,line surges etc, it was common for one of these fuses to blow, saving what often was 50amp, 100 amp drives.'
M.

 

Mantech or RS Electronics. Both will deliver but RS don't deliver to a post box