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Home > Archive > Electrical Engineering > July 2007 > Melting fuses
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| Wilscombe 2007-07-24, 9:25 am |
| I have a brand new (Chinese) electric bicycle that melts (rather than
blows) the 30 amp spade fuse every time I use it. Voltage is 36v and
the motor is 180 watts. A 40amp fuse is available by special order
but I am reluctant to use one without specialist advice.
Just to clarify; the spade fuse is the standard one used on 12v
automotive systems.
Any thoughts would be appreciated.
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| Salmon Egg 2007-07-24, 1:25 pm |
| On 7/24/07 6:03 AM, in article
1185282208.766049.26980@g4g2000hsf.googlegroups.com, "Wilscombe"
<Wilsc0mbe@googlemail.com> wrote:
> I have a brand new (Chinese) electric bicycle that melts (rather than
> blows) the 30 amp spade fuse every time I use it. Voltage is 36v and
> the motor is 180 watts. A 40amp fuse is available by special order
> but I am reluctant to use one without specialist advice.
> Just to clarify; the spade fuse is the standard one used on 12v
> automotive systems.
> Any thoughts would be appreciated.
>
Off the top of my head, a 180 watt motor is pretty underpowered for the
application. Moreover, the voltage and current you list indicates power
capability of close to 1000W. Check your numbers.
Bill
--
If intelligent design trumps evolution, please explain hemorrhoids.
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| Rheilly Phoull 2007-07-25, 9:25 am |
|
"Salmon Egg" <salmonegg@sbcglobal.net> wrote in message
news:C2CB7241.8C555%salmonegg@sbcglobal.net...
> On 7/24/07 6:03 AM, in article
> 1185282208.766049.26980@g4g2000hsf.googlegroups.com, "Wilscombe"
> <Wilsc0mbe@googlemail.com> wrote:
>
> Off the top of my head, a 180 watt motor is pretty underpowered for the
> application. Moreover, the voltage and current you list indicates power
> capability of close to 1000W. Check your numbers.
>
> Bill
> --
> If intelligent design trumps evolution, please explain hemorrhoids.
>
>
Errmm, that 1kw would be at the fuse rating. The actual running current
would be more like 5amp once up and running. Noting the source of
manufacture there can be disrepancies on name plate data and mebbe the
startup current is taking the fuse or there is a fault. On the other hand
'melting' the fuse is usually overload rather than a fault. Perhaps you may
be able to borrow an ammeter and check the draw of the motor ?
--
Cheers .......... Rheilly P
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| Palindrome 2007-07-25, 9:25 am |
| Wilscombe wrote:
> I have a brand new (Chinese) electric bicycle that melts (rather than
> blows) the 30 amp spade fuse every time I use it. Voltage is 36v and
> the motor is 180 watts. A 40amp fuse is available by special order
> but I am reluctant to use one without specialist advice.
> Just to clarify; the spade fuse is the standard one used on 12v
> automotive systems.
> Any thoughts would be appreciated.
>
I assume that you mean that the plastic body of the fuse is melting?
Which is usually down to a faulty fuseholder either not making good
contact with the fuse or, IME more often, a bad crimp between the
conductors and the fuse holder contacts. This produces a high resistance
and enough heat to melt the fuseholder.
The solution is to replace the fuse-holder. I would suggest using a
resettable over-current trip rather than the blade fuse. Or, at least,
carry a few spares.
--
Sue
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| Wilscombe 2007-07-26, 9:25 am |
| On Jul 24, 5:09 pm, Salmon Egg <salmon...@sbcglobal.net> wrote:
> On 7/24/07 6:03 AM, in article
> 1185282208.766049.26...@g4g2000hsf.googlegroups.com, "Wilscombe"
>
> <Wilsc0...@googlemail.com> wrote:
>
> Off the top of my head, a 180 watt motor is pretty underpowered for the
> application. Moreover, the voltage and current you list indicates power
> capability of close to 1000W. Check your numbers.
>
> Bill
> --
> If intelligent design trumps evolution, please explain hemorrhoids.
Thanks for your thoughts. A motor of 200/180W is pretty standard for
the "electrically-assisted" bikes in the UK. My old bike has a faulty
200W motor and it goes like a train. I understand that torque is the
prime requirement.
Since posing the question I've found that the power display on the
handlebars goes out when pressure is put on the saddle. (Weird or
what!) So it looks like there is a short to the frame - somewhere.
I think the answer must be that the 40amp fuse is not an option,it's
back to the shop for a wiring check.
Thanks again.
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"Palindrome" <me9@privacy.net> wrote in message
news:KEFpi.207690$qT.128012@fe06.news.easynews.com...
> Wilscombe wrote:
>
> I assume that you mean that the plastic body of the fuse is melting? Which
> is usually down to a faulty fuseholder either not making good contact with
> the fuse or, IME more often, a bad crimp between the conductors and the
> fuse holder contacts. This produces a high resistance and enough heat to
> melt the fuseholder.
>
> The solution is to replace the fuse-holder. I would suggest using a
> resettable over-current trip rather than the blade fuse. Or, at least,
> carry a few spares.
> --
> Sue
>
Or use the correct 36v fuse and not a 12v one
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