VFD Fuse Trouble

[Stark Knives]

The VFD on my grinder has been blowing lately and when I opened up the box, the fuse holder appears to be corroded/blown. How do you all recommend I fix this? I'm don't have much electrical experience so I wasn't sure where to start.

Thanks!

 

[DAMNENG]

If you can post a photo of the fuse holder or a good one just like it and the dimensions we might be able to make an intelligent suggestion.

 

[Kevin McGovern]

Woah! That can be easily replaced just by taking the terminal off one end and unplugging it from the other. What I'm more concerned with is why that wire is burned up like that. Did you replace the fuse since you've had it and and if so did you replace it with a fuse that was higher than it should have been

 

[Stark Knives]

Woah! That can be easily replaced just by taking the terminal off one end and unplugging it from the other. What I'm more concerned with is why that wire is burned up like that. Did you replace the fuse since you've had it and and if so did you replace it with a fuse that was higher than it should have been

I have replaced the fuse inside and I'm pretty sure that it was the correct amp type. I can double check that though.

 

[Lieblad]

Yuk !
Obviously its getting too hot. I suspect poor connections within the fuseholder rather it being strictly overfused.
You really need to know the max. current what that VFD is capable to carry and how much current your motor is drawing.
Select fuse size accordingly.

Just for fun Google images of "melted fuseholder", Mostly its automotive failures, but mains voltages too. Just illustrates low quality fuseholders and other elecrto-crap is abundant.

 

[DAMNENG]

Stark
First let me say that I didn't notice the photo before I made my last post.
Looking at the melted insulation, it appears that the wire which runs to terminal strip got hotter than the one on the other end of the fuse holder. I would guess the lug wasn't tight on the terminal strip or the lug wasn't properly crimped. This would cause a high resistance joint which could lead to high temps at high currents.

 

[ron_m80]

I would assume, but not without checking afterward, that you have a substandard fuse holder in there.

I say that because the current in that supply circuit would be the same throughout. All of the heat and damage is localized before the terminal and after the fuse holder crimp connection. The rest of the wiring looks fine, not even a hint of heat damage.

 

[Stark Knives]

Thanks for the help everyone! I ended up just having my cousin come and directly wire it and it's been working well so far.

 

[Stacy E. Apelt - Bladesmith]

WOAH!!!!!

You don't EVER want to hardwire a circuit to replace/bypass a fuse. The fuse is there to tell you something is wrong. With it hardwired, the next indication may be the whole unit going up in smoke.

 

[Drew Riley]

WOAH!!!!!

You don't EVER want to hardwire a circuit to replace/bypass a fuse. The fuse is there to tell you something is wrong. With it hardwired, the next indication may be the whole unit going up in smoke.

What if I have a piece of pipe that's roughly the same size as the 50 amp fuse it's replacing???

In all seriousness, and while I would normally agree with you, I'm not sure why the inline fuse was there to begin with. I'm assuming they read the wiring instructions where it says "Be sure to properly fuse each AC Line conductor that is not at ground potential" and perhaps misunderstood? As long as circuit that it's plugged (or possibly hardwired) into has an appropriately rated circuit breaker for the conductors being used, the fuse really isn't necessary. The drive itself should have some built in protection in the case of overcurrent or overtemp faults, not that these should be relied on exclusively or repeatedly.

Now, concerning the melted insulation, I'd certainly double check the incoming current with an ammeter, but it looks to me like somebody simply went overboard with a soldering iron when they installed the inline fuse holder. Another possibility is a poor connection that's causing a bit more heat than normal.

At any rate, I'd personally cut out the fuse, wire as normal, and do a final sanity check with my clamp meter when the unit powered up, as well as when it was running, just to make sure nothing was out of whack. Since OP claims to have little or no electrical experience, I'd find somebody who does, to evaluate the circuit and re-wire the VFD appropriately.

 

[Stacy E. Apelt - Bladesmith]

The power circuit will blow at , lets say 30 amps. If there is an internal issue with the VFD, it may go up in smoke and when it has fully destroyed itself, still not have tripped the breaker.

When the instructions called for fusing all incoming power lines, that is because all power carrying lines need to be fuse protected at the VFD. Normally, you use a two fuse block and connect the block to the power terminals on the circuit board. I don't know that I have ever seen one done with that type in-line fuse holder. As long as the wire gauge is sufficient, it should work, but I suspect it was an automotive type fuse holder and not one with a sufficiently heavy wire for a 220 volt connection.

My recommendation is to get a two fuse block and connect it to the power from the switch on one side and the circuit board on the other. Mount the block in the cabinet near where the power cord comes in.

 

[ron_m80]

I think he's ok. KB series drives say "circuit breaker or fuse", and list fairly high input amperage for fusing.

 

[Stacy E. Apelt - Bladesmith]

I don't agree, I pop a fuse on my drive sometimes when hogging. The line breaker is far higher rated than the 15 amp fuse. If there was not that fuse there, the VFD might overheat and burn up long before a 30 amp wall breaker pops.

I did electronice for a good while, including the engineering aspect of it. A properly rated fuse at the device is a requirement for any electronic device. On 220VAC circuits and three phase direct devices, each power input leg has its own fuse. The only incoming wire not fused is the neutral/ground.