Bandsaw Blowing Fuses

[Daniel.l]

Hi All,

This time last year I made Matthias Wandels 20" bandsaw. It has been fantastic and working very well except a couple of times now it has blown a fuse in the plug.
It has a 2hp single phase motor wired to a nvr switch
The first time it blew the fuse was on startup it kicked for a second and went and the second time it was just gone when I went to start.
If its a starting load problem as the wheels are quite heavy I'm wondering would something like this help?

https://ie.rs-online.com/web/p/motor-starters/3305358
If anyone has any experience with this or electrics in general I would greatly appreciate the advice. I have never installed anything like this before

 

[NormanB]

Have you checked the motor capacitor?

 

[guineafowl21]

Check for excessive resistance in the drivetrain - stiff bearings, overtight belts, etc.

That soft starter looks like it would do the job, but it can get tedious, waiting for a machine to spin up when doing start-stop repetitive work. Popping the fuse on start-up could indicate the machine is just on the borderline for use with a standard domestic socket. In the long term, you could get heat damage to the socket and plug top.

A more widely-used solution is to get a 16A blue socket installed (preferably with an isolator switch), if possible with a C-type breaker (as opposed to B), and install a proper NVR switch with overload on the machine. A decent electrician would sort all that easily.

 

[Sachakins]

https://www.ebay.co.uk/itm/Soft-Sta...2349624.m46890.l49286&mkrid=710-127635-2958-0

 

[Ttrees]

I've not seen starters for single phase induction motors before, not that I'm anything but a joe soap.
Would have very much thought that would have been mentioned on the induction motors issue 3 article which can be found at "the other place"


Might be worth looking into finding some cheap 3 phase motors.... some of which can run on 240v
these are called dual voltage motors, and can be run with a hundred quid VFD/inverter.
You'll be able to go up to 3 hp then, and have an adjustable soft start at the touch of a button.

Love to see the machine sometime
All the best

 

[eribaMotters]

I think this is down to the quality of your motor. On 3 pin plugs I have 3hp motors on a Startrite P/T and a Elektra Spindle Moulder along with a 2hp motor on my Startrite Bandsaw. None of these machines give me a problem. On my 1.5hp JET dust extractor I do have issues. This blows 13 amp fuses on a seemingly random basis. When a moto starts up it can draw 4 to 6 times what it will run at. This is what blows the fuse.
When I wired up my workshop I had C type breakers fitted to my consumer unit. I cannot recall one of these tripping.

Colin

 

[Ttrees]

@eribaMotters Is that when blast gates are shut off, or all open?
Maybe @Inspector if he's around can advise on the best practice, but I know these can over draw from too much air flow.
Whether there's a minimum requirement I don't know.

Back to the original query, sorry for derailment.
Heat can be another factor, although I wouldn't know much about that.

Could pole number be a factor, i.e
Is there more current required for a 2 pole (say 2840 to 3000 RPM)
than there is for a 4 pole motor (say around half those figures)

This IS a TEFC motor, Isn't it?

I've heard it mentioned before, albeit only once, not so sure how big of a factor that is.

If all else fails myfordman (Bob) may come to the rescue.
Tom

 

[Spectric]

Dont just assume it is an electrical fault, fuses will blow for several reasons so take a logical approach and one thing at a time. The Record BS400 has a 2Hp single phase motor and runs happily from a 13 amp socket, and as Eriba Motors has said he also runs several machines on 13 amp sockets so I would initially assume your issue is mechanical and so the first thing to try is remove the blade and see what happens running the motor load free. Then check all parts rotate freely, ie no dust in bearings etc and then tell us what happens.

A softstarter is a good approach, readily available for single phase and it will reduce startup current and give the machine an easier life, it is the difference between waking up with an alarm clock and having a bucket of cold water thrown over you but it is not really solving the problem but circumnavigating it.

 

[Daniel.l]

Thanks for all your replies sorry I'm a bit late replying I've been busy at work.
I bought the motor brand new this time last year
https://www.electrotechdrives.co.uk/product/1-5kw-2-hp-2800rpm-240v-electric-motor-single-phase/I'm presume the capacitor is good because once the fuse is changed it works perfectly again. I've used it moderately in the last year but I was cutting quite a deep timber 300mm before it blew and it finished the cut no bother it was just the next time I went to turn it on there was nothing.
A 16amp socket and c type breaker would be good but at the moment I'm looking for a faster cheaper resolution.
3 phase would also be above what I'd like to spend.
I'll must check all the bearings tomorrow and see how free they are I can spin the blade free by hand with no strange noises however I haven't gotten around to making the dust extraction for it so maybe that's causing issues.

Also the wheels are quite heavy so it is a fair amount of weight to start to spin I went with MDF wheels after watching Marius hornbergers approach at building it, as MDF is much easier to balance due to less pockets.
My thinking was weight on startup initially and the soft start would reduce the load
I should probably run some tests and see what amps it pulls when starting is that something I could do with a multimeter?

Here's some pictures of the wheels I took last year. I did promise a post about the bandsaw a while back but I haven't actually finished it
It needs dust extraction a belt cover and painting

 

[eribaMotters]

I'm just thinking back to my late departed father. He was an electrical engineer with the CEGB, his claim to fame wiring up a power station.
I'd bought a second hand 3 Kw single phase Mulico circular saw bench and it was blowing fuses. This was before the day of nice modern consumer units and C type breakers. He turns up and swaps the fuse over in the 3 pin plug and turns the saw on whilst holding a fancy induction load gizmo meter thingy around the lead. The saw drew over 45 amps on start up, did not trip and ran a treat.
The trick was he'd drilled out a 13amp fuse and soldered a length of 20amp fuse wire into through the fuse body. Who was I to question him. It ran a treat in all the time I owned the machine. Dad assured me it was perfectly safe as the saw was running at about 12amp under load, according to his gizmo, the fuse in the board was 20 amp and the 3 core ring main cable could cope with far higher. The saws 3 pin plug was also 2.5mm 3 core flex.

Colin

 

[Daniel.l]

Also just something else to note when making the pulley wheel I had some issues at the beginning with the belt slipping when starting its quite fast so I added some stixall to the birch ply pulley to add grip and also tightened the belt tension, I don't get slippage anymore but the belt might be too tight this also could be solved with a soft starter. At the time of making I couldn't find one but I just came across another forum which linked that one above

 

[Daniel.l]

I don't think Id be confident enough to do that

 

[Ttrees]

Likely not of much interest, just felt obliged to add...
If you do ever decide to go the vfd / inverter route in future, as you may have seen Marius's bandsaw video on the subject
Take heed that he didn't warn that if the motor needs the rotation reversed,
It's very important to wait until the VFD powers down!

It does take a wee while for those massive capacitors to drain off after being unplugged from the wall,
so don't touch those input or output wires until it is safe to do so.
Have a read of Bob's freely available induction motor document for pretty much all common motors, switches, and all about setting up VFD/inverters.
Best reading I've came across on the subject.

Sorry I can't help with any guidance for you, as I guess you just want to get this sorted.
Good luck
Eager in seeing the results of the saw, when it's all done.
Looks a good job

All the best
Tom

 

[Spectric]

but the belt might be too tight this also could be solved with a soft starter.

The solution for an overtight belt is to retension it correctly, an overtight belt will cause premature wear of bearings and place undue stress on the machine.

As for heavy wheels, that is a bonus and many machines use cast iron because once spining they are a source of energy, in essence a flywheel so again you have issues elsewhere.

I would not get to hung up with capacitors storing any big charge in an Ac circuit, they will charge / discharge every half cycle which with a 50Hz supply is 10mS and the voltage varies constantly with the polarity changing every half cycle. If the circuit is Dc then be very aware, if you have ever been inside an old Tv you know about the flyback circuit that could make you jump!

 

[Knox-on-Wood]

I had a similar problem with a Record BS400. A simple fix is to buy a 13amp delay fuse. I got mine on Amazon. I have used tis for over 10 years with no problems over tripping.

 

[Spectric]

Interesting, never had a fuse blow on my BS400 but then I know all my circuit impedances within the installation are low so it does show how peoples instalations must vary and not just in run lengths. Using a slow blow fuse is ok so long as you know the instalation is upto standard.