(Topic ID: 325661)

Fuse value to protect coil

By Seamlesswall

4 months ago



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#1 4 months ago

If a stepper coil is drawing 1.9 amps, what is a good value fuse to protect it? I put a 1.5A SB and yes the fuse popped, but that was after the coil bit the dust.

#2 4 months ago
Quoted from Seamlesswall:

If a stepper coil is drawing 1.9 amps, what is a good value fuse to protect it? I put a 1.5A SB and yes the fuse popped, but that was after the coil bit the dust.

If the 1.9 amps is a "continuous" current then it is no surprise that the 1.5A SB fuse blew. Is this a current you measured, or some printed rating of the coil? I think you have to go at least 2.0A for the rating, and the SB can handle some instantaneous spikes that go higher than its rated value. There are sets of complex calculations for pulses and currents, but for a simple stepper that is probably overkill.

#3 4 months ago

I'm not sure you can reliably protect a coil with a standard or slow blow fuse. The problem is that the coil won't necessarily exceed the fuse amperage just because it is held in (stuck on). It will however build up heat to the point that it melts, shorts out and blows the fuse. Which is far too late to do any good. You would probably need some sort of thermal fuse rated at a predetermined temperature.

#4 4 months ago

Agree. The fuse is more to protect circuit and wiring, and from a fire, in the event of a catastrophic failure. Not really meant to protect the stepper coil.

#5 4 months ago
Quoted from Seamlesswall:

If a stepper coil is drawing 1.9 amps, what is a good value fuse to protect it? I put a 1.5A SB and yes the fuse popped, but that was after the coil bit the dust.

Might be a good idea to name the game and what the stepper is for.

#6 4 months ago
Quoted from edednedy:

You would probably need some sort of thermal fuse rated at a predetermined temperature.

That idea had crossed my mind and I will look into that option.

Quoted from wayout440:

The fuse is more to protect circuit and wiring, and from a fire, in the event of a catastrophic failure. Not really meant to protect the stepper coil.

The only upside is that the coil fries then fuse blows, but no smoke to frighten customers and Marco makes money.

Quoted from EMsInKC:

Might be a good idea to name the game and what the stepper is for.

Paratrooper as listed at top.
Paratrooper has been problematic from day one, if it were not such an interesting and forward thinking game, I'd suggest it gone. All of the problems have been sporadic thus hard to isolate and most issues lead to (because of the design) burned coils. I don't remember all of the fixes I have done but I recall at least a couple of issues were carbonized contact buttons on leafs and magnetized coils in relays. This latest issue was on the 100,000 unit in the upper right. (notice how crispy the stepper coil is in this pic from the database and the missing bell coil as that must have gone up in smoke, these two coils are related and always fry together.) Our Paratrooper can run for months with no issues, then the dreaded "Don't flip out" sign ends up on it. So, this latest was an easy find, I hand activated the advance coil, the crispy one, and would not get far enough to go to the next cog. That turned out to be a worn pivot point (upper left on the unit) which shows a screw there. We have a stamped rivet. Right now it's McGivered and working. I believe we have a call into PBR to
see if they have a part otherwise it's Zen time to come up with a permanent solution.
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