Author Topic: poorly seig c3  (Read 987 times)

Offline awemawson

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Re: poorly seig c3
« Reply #25 on: June 08, 2017, 08:43:21 AM »
And does the beast now turn ?
Andrew Mawson
East Sussex

Offline davidcurtis021

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Re: poorly seig c3
« Reply #26 on: June 08, 2017, 08:53:37 AM »
And does the beast now turn ?

yes it does. Thank you for asking

Offline John Rudd

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Re: poorly seig c3
« Reply #27 on: June 08, 2017, 09:00:18 AM »
Just make sure you fit the new fuseholder.....and... Fwiw, despite what fuse is fitted, change it to a 3 amp fuse.....These machines tend to be shipped with fuses with a rating higher than necessary.
The result is either a blown control board or motor or both.....you could also check the fuse in the mains plug....again no more than 3 amps should be sufficient
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Offline davidcurtis021

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Re: poorly seig c3
« Reply #28 on: June 08, 2017, 09:09:45 AM »
Just make sure you fit the new fuseholder.....and... Fwiw, despite what fuse is fitted, change it to a 3 amp fuse.....These machines tend to be shipped with fuses with a rating higher than necessary.
The result is either a blown control board or motor or both.....you could also check the fuse in the mains plug....again no more than 3 amps should be sufficient

thanks John

i know for definate that the fuse in the plug is a 5 amp so i'll do that straight away.

Offline John Rudd

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Re: poorly seig c3
« Reply #29 on: June 08, 2017, 09:14:33 AM »
So, what is the justification for a smaller fuse?
Simply put, watts is volt x amps.
The motors on these small lathes are around 300-400 watts. So at max load they will consume no more than about 2 amps....Generally the speed controllers have in built protection to avoid over current, but should something  go awry, last level of protection is the fuse....

Thats my take on it and as it happens, is the same approach adopted by Warco, I'm told from sources on another forum
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Offline PekkaNF

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Re: poorly seig c3
« Reply #30 on: June 08, 2017, 11:21:23 AM »
Time-current characteristics
http://www.littelfuse.com/~/media/automotive/catalogs/littelfuse_fuseology.pdf

Looks like 3,15A fuse blows about 10A in 0,1 sec, would that card withstand 30A for 0,01s?
http://www.farnell.com/datasheets/1447843.pdf

Generally those fuses are fine when they are chosen to blow out on wire short circuit and prevent wires. To dimension these glass tube fuses to protect electronic circuit on small over current or surge load is not easy.

Another issue is selectivity. The mill fuse should blow before plug fuse and plug fuse should blow before mains fuse. Two fuses near same melting current is a bad idea.

Pekka


Offline John Rudd

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Re: poorly seig c3
« Reply #31 on: June 08, 2017, 12:34:50 PM »


Generally those fuses are fine when they are chosen to blow out on wire short circuit and prevent wires. To dimension these glass tube fuses to protect electronic circuit on small over current or surge load is not easy.

Another issue is selectivity. The mill fuse should blow before plug fuse and plug fuse should blow before mains fuse. Two fuses near same melting current is a bad idea.

Pekka

Pekka,
I was merely suggesting that to prolong the life of the machine, the the op change the fuses to a value lower than those originally fitted.
It is cheaper to replace a blown fuse in the event of a fault than have to buy a new motor or pcb.

The manufacturers of these machines will fit protective fuses, albeit with values that are far too high...the number of machines that have come my way for repair have fuses that are far in excess and have not afforded any protection to the motor or electronics....
I did not make my recommendations on a whim, there is evidence from other forums, that members there have had the same recommendation from a major machine tool supplier....
At the end of the day, its no skin off my nose if the op does nothing..however, if I carry out repairs to a machine, I ensure that the equipment fuses are adequate and fit for purpose in order tomoffer any guarantee of repair.

Rant over....
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Offline PekkaNF

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Re: poorly seig c3
« Reply #32 on: June 08, 2017, 04:07:13 PM »
Something lost in translation :wave:

My intention was not to criticize your choice of fuse on this particular instant. Merely to point out some points to greater public that there is some logic on fuse selection.

I have noticed the same thing about fuse size, maybe they rather sell new card/motor than listen rap about burnt fuses. Also the mill might not reach rated power with smaller fuse, but there is risk of burning something under other circumstances.

Cheers,
pekka

Offline tom osselton

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Re: poorly seig c3
« Reply #33 on: June 09, 2017, 12:44:56 AM »
That happened to me on my Craftex mill the doughnut wire wrapped thing (choke?) unsoldered itself and dropped onto wires below! They gave me a different board but the tack has not worked since.