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With what can I replace this old glass tube fuse?

Original fuse: glass tube fuse with the engravings "UEC 10A."

It is from a industrial motorized device perhaps 15-20 years old from Japan.

I have tried F10AL250V fuses, but it blew these new fuses. I don't think it's a problem with the device (e.g., a short circuit) as I have a second, identical version of this device that also blows these fuses. I cannot find documentation for this device.

Below is the original blown fuse that worked with the machine. 6x30mm.

Original blown fuse that worked with the machine. 6x30mm.

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    \$\begingroup\$ Have you tried slow blow not fast blow fuses? \$\endgroup\$
    – Passerby
    Commented May 14, 2023 at 20:38
  • \$\begingroup\$ Slow blow fuses are a must for starting any size of motor. \$\endgroup\$
    – user16324
    Commented May 14, 2023 at 20:44
  • \$\begingroup\$ I have not -- will this fry the device if it doesn't use slow blow fuses? \$\endgroup\$
    – myflow
    Commented May 14, 2023 at 20:45
  • \$\begingroup\$ It will just likely blow the fast acting fuses quite fast. \$\endgroup\$
    – Justme
    Commented May 14, 2023 at 20:53
  • \$\begingroup\$ If I try a slow blow fuse and the device doesn't use slow blow fuses, will it destroy the device? \$\endgroup\$
    – myflow
    Commented May 14, 2023 at 20:56

3 Answers 3

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Fast-action glass fuses are suitable for resistive applications, that do not involve high switch-on surge currents.

Slow-action glass fuses are intended for handling high switch-on surge currents, drawn at motor start or power supply switch-on.

The F10AL250V is a fast-action fuse.

Your motor control application requires a T10AL250VP slow-action fuse.

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  • \$\begingroup\$ I attached an image of the blown fuse that worked with the machine -- does it look like possibly a time delay/slow blow fuse? \$\endgroup\$
    – myflow
    Commented May 15, 2023 at 17:14
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You can try a slow-blow fuse. There do not appear to be medium blow fuses currently easily available in that size and rating.

Slow blow is typically adequate to protect wiring and things like motors and transformers, but may allow more damage to your equipment if something else is wrong (for example, to semiconductors).

Unless there is a lot more information available and the knowledge to apply it, I don't see a whole lot of other options open, other than the obvious one of trying to source an exact replacement from some unknown Asian manufacturer (who might well be defunct or have changed hands one more times by now).

I don't suggest increasing the fuse rating and staying with fast-blow, that's for sure.

The fuse pictured does not look like a slow-blow to me (typically they have a coil or spring like structure inside) but it may be sufficiently different from other fast-blow fuses to work whereas the ones you can buy don't.

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  • \$\begingroup\$ Thank you. I think the Asian manufacturer is long gone unfortunately. Does it look like a "medium blow" fuse? I've never even heard of those -- were those more common decades ago? \$\endgroup\$
    – myflow
    Commented May 15, 2023 at 19:35
  • \$\begingroup\$ @myflow They're listed now, but I don't see any in stock at Digikey in your size and rating. I didn't look very hard. \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented May 15, 2023 at 22:12
  • \$\begingroup\$ I did try a slow blow (T10A250V) and unfortunately both machines blew those fuses. I can only conclude both machines independently acquired shorts, which surprises me as I was informed the second machine was operational. Are there any other explanations aside from both having shorts? \$\endgroup\$
    – myflow
    Commented May 18, 2023 at 19:40
  • \$\begingroup\$ Slow blow fuse of the original rating failing instantly is an indication something is seriously wrong. It might not be a direct short, but something is causing a large overload current. \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented May 18, 2023 at 19:45
  • \$\begingroup\$ I see. Would it be possible to give some examples of what might cause a large current overload so I can investigate that possibility? \$\endgroup\$
    – myflow
    Commented May 18, 2023 at 19:49
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The fuse in the photo shows what looks like a short in the circuit (or too low amp rating). Even a fast blow fuse won't usually melt and carbonize the glass. Usually, a fast blow rated for the circuit current will work for a few cycles before breaking the wire.

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