Catastrophic Fuse Failures on Metal Halide Circuits

[GotShocked]

We are experiencing repeated failures of Littelfuse CCMR 30A fuses within lighting control panels that serve 1000W Metal Halide lighting circuits. See attached photo. The fuses appear to be properly sized for short circuit current, in-rush & continuous loads. We can find not evidence of water intrusion or rodent getting across the fuses or other causes. Any ideas? We are considering temporary resonance as a possibility?

 

[ptonsparky]

Heavy fog will do it. How often is repeated?

 

[K8MHZ]

It looks like a bad connection at the bottom. One of the screws is actually gone, either it fell out or got vaporized. I would like to see pics of the others if this happened more than once.

 

[JFletcher]

Weak/corroded fuseholder not making good contact?

 

[GotShocked]

Another Failure Photo

Another Failure Photo

Here is another photo of a past failure, I'm looking for others. There have been other failure events where the fuses blew less catastrophically but multiple circuit fuses were blown. Just before the recent failure, (4) fuses were blown, one ruptured. Following that event, we had the electricians check all of the connections, fuse holders, etc. Two weeks later, disaster!

 

[ptonsparky]

It’s odd for fuses like these to fail in this manner. What is happening on the load side and what is the available fault current at this panel?

Who all has access and what do their testers or screwdrivers look like?

 

[GotShocked]

Previous Photo

Previous Photo

Attached is a previous photo, I am looking for others.

 

[ptonsparky]

There is no load side damage anywhere?

 

[ptonsparky]

Have you sent these pictures to the manufacturer’s fuse rep? You should be on a first name basis with him by now.

 

[ptonsparky]

The mounting screws for the fuse holders may be a bit on the large size. Try using the enclosed holders that clip on a din rail. We happen to use EHCC series from AD.

 

[GoldDigger]

Are the fuses and holders rated for the applied voltage and current, taking into consideration the potential inductive kick when the fuse opens?
It seems to me that the damage resulted from a persistent arc, or arc flash, being triggered by the fuse opening. That or really excessive voltage to ground on the circuit.
Why the fuse opened in the first place is a separate question. Does the failure mode of metal halide lamps include a transient current surge such as what happens with large filament incandescent?

 

[JFletcher]

OP said no evidence of rodents or moisture... what about insects? If a moth were to bridge phases at the fuses/holders, would it not initiate an arc flash, blow up, and vaporize, leaving no trace of insect?

 

[K8MHZ]

I don't know if this is relevant or not, but CCMR fuses are meant for motor circuits:

CCMR Series dual element, time delay fuses are recommend for space-saving protection of motor circuits up to 40 HP

• Only true dual-element time-delay CC fuses specifically engineered for motor branch circuit protection.
• Provide Type II protection (no damage) to both NEMA-rated and the more sensitive IEC (International Electromechanical Commission) type motor circuit components.

http://www.littelfuse.com/products/fuses/industrial-power-fuses/class-cc-fuses/ccmr.aspx

 

[K8MHZ]

I would think these fuses would be the best choice for the application:

KLDR fuses are time-delay fuses designed to protect control transformers, solenoids and similar inductive components with high magnetizing currents during the first half-cycle. They provide excellent protection of motor branch circuits containing IEC or NEMA rated motorcontrollers or contactors.

http://www.littelfuse.com/~/media/e...d-ul-fuses/littelfuse_fuse_klkr_datasheet.pdf

 

[Sahib]

The fuse lot is defective. Check remaining spare fuses for any appreciable increase in resistance.

 

[retirede]

The fuse lot is defective. Check remaining spare fuses for any appreciable increase in resistance.

I’m skeptical.

 

[ptonsparky]

I’m skeptical.

. I agree.
Something started an arc and the fuse, fuse holder and wires happened to be close by. An arc fault blows a fuse via heat alone eventually, maybe. Generally it runs out of things close by to sustain the arc.

Change what obviously has failed miserably.

 

[Sahib]

If arc flash were cause, rather than effect, the severity of damage in the two photos of OP would be almost same. But it is not so. So it may be that over heating of fuse or some other component initiated the damage.

 

[kwired]

. I agree.
Something started an arc and the fuse, fuse holder and wires happened to be close by. An arc fault blows a fuse via heat alone eventually, maybe. Generally it runs out of things close by to sustain the arc.

Change what obviously has failed miserably.

Correct, a possibility is poor termination, develops heat, fuseholder starts to break down from that heat, and especially on 480/277 systems will fail in this kind of manner once that flashover point is reached.

 

[ptonsparky]

Similar to this with optional lug kit for feed. Torque connections.