test a capacitor

Jackrae · 2 Jun 2015

1Kw single phase motor should be easy to start. 300microfard for that size of motor seems a bit odd (large) but so does using a 125VAC capacitor on a 240 volt system - even if it's in series with a winding.

To check out your problem of intermittent tripping (as against a constant fault) requires some real test equipment. As had been said earlier a megger is essential to check for earth leakage.

Do you have a circuit of the planer wiring.
Can you supply a photograph of the actual capacitor (with writing)
Is the planer motor an induction motor or a universal one (has brushes)

JW2 I'd inadvertently used 330 in my calculation rather than 300, hence 9.6 vs the correct 10.6

Harbourwoodwork · 2 Jun 2015

Conny
I could try that
Cheers Ian

JohnW2 · 2 Jun 2015

Jackrae said:
JW2 I'd inadvertently used 330 in my calculation rather than 300, hence 9.6 vs the correct 10.6

I can't really blame you for that 330μF is a very familiar E12 preferred value, whereas 300μF is not, as far as I am aware, any sort of preferred value not even E192)!

I still doubt that any 'supply fuse' would have blown with 22A (we recently concluded that even a BS1362 13A fuse would never blow with less than about 21A - and it would take 'hours' at that current) - but, in any event, it now seems clear that it is actually an RCD (or two RCDs) which is tripping in the OP's case.

Kind Regards, John

plugwash · 2 Jun 2015

JohnW2 said:
300μF is not, as far as I am aware, any sort of preferred value not even E192)!

It is in the E24 series.

Note that E6 is a subset of E12 which is a subset of E24 and E48 is a subset of E96 which is a subset of E192 but E6/E12/E24 are not subsets of E48/E96/E192

Harbourwoodwork · 2 Jun 2015

I had no luck uploading a pic
This is all that is written on the Cap

SSEC
MOTOR STARTING
CAPACITOR
CAP. 300 MFD
W. V. 125 VAC

JohnW2 · 2 Jun 2015

plugwash said:
JohnW2 said:

300μF is not, as far as I am aware, any sort of preferred value not even E192)!

Click to expand...

It is in the E24 series.

So it is. That's news to me, and I certainly stick to my view that (at least for me!) it's not a 'familiar' value!

plugwash said:
Note that E6 is a subset of E12 which is a subset of E24 and E48 is a subset of E96 which is a subset of E192 but E6/E12/E24 are not subsets of E48/E96/E192

Goodness - one learns something every day

I've never really had reason to study this too deeply, but confess that I'd always assumed that all were subsets of E192. That's why (as it turns out, foolishly!) I had a quick look at just E192 before I posted my last message!!

Kind Regards, John

plugwash · 3 Jun 2015

JohnW2";p="3397390 said:
plugwash said:

JohnW2 said:

300μF is not, as far as I am aware, any sort of preferred value not even E192)!

Click to expand...

It is in the E24 series.

Click to expand...

So it is. That's news to me, and I certainly stick to my view that (at least for me!) it's not a 'familiar' value!

Not so much capacitors (I don't use many capacitors in situations where the exact capactance matters much) but with resistors I find myself using 2K and 3K in my designs quite a lot to make nice ratios.

plugwash";p="3397380 said:
Goodness - one learns something every day I've never really had reason to study this too deeply, but confess that I'd always assumed that all were subsets of E192. That's why (as it turns out, foolishly!) I had a quick look at just E192 before I posted my last message!!

Yeah, the E series are somewhat strange.

E6/E12/E24 have two digit numbers, E48/E96/E192 have three digit numbers.

Both sets are approximately geometric but for some unknown reason they don't quite match what you get if you simply take a geometric sequence and round it to the requisite number of digits. Theres some interesting speculation about how they may have been derived at http://en.wikipedia.org/wiki/Talk:Preferred_number#Resistor_series[/quote][/quote]

JohnW2 · 3 Jun 2015

plugwash said:
It is in the E24 series.

So it is. That's news to me, and I certainly stick to my view that (at least for me!) it's not a 'familiar' value!

Click to expand...

Not so much capacitors (I don't use many capacitors in situations where the exact capactance matters much) but with resistors I find myself using 2K and 3K in my designs quite a lot to make nice ratios.

I've certainly used 'round figure' values of resistors, in such situations as you describe (to create divider chains etc.), but I certainly don't keep them 'in stock' and had rather assumed that, when I bought them, they were 'non-preferred-value specials'!

plugwash said:
Yeah, the E series are somewhat strange. E6/E12/E24 have two digit numbers, E48/E96/E192 have three digit numbers.

That much makes sense - the 'longer' series probably need more precision, otherwise the possible values would be restricted.

plugwash said:
Both sets are approximately geometric but for some unknown reason they don't quite match what you get if you simply take a geometric sequence and round it to the requisite number of digits. Theres some interesting speculation about how they may have been derived at http://en.wikipedia.org/wiki/Talk:Preferred_number#Resistor_series[/QUOTE]
That sounds familiar, but I'll have another look!

Kind Regards, John

ban-all-sheds · 3 Jun 2015

JohnW2 said:
and it's still an abbeviation which is not uncommonly used:

It's wrong.

ban-all-sheds · 3 Jun 2015

plugwash said:
Sadly in the context of capacitors using "m" to mean micro is an established practice

It's wrong.

ban-all-sheds · 3 Jun 2015

JohnW2 said:
This document says:

...Short forms for micromicrofarad include pF, mmfd, MMFD, MMF, uuF (note the "u", not "μ") and PF....

Click to expand...

.

At least 4 of those are wrong.

ban-all-sheds · 3 Jun 2015

JohnW2 said:
deca- and deci- are also potentially ambiguous, but the former is rarely used and, IIRC, if used is abbreviated to "da"

It is.

And that would be unnecessary and deci-/deca- confusion removed if they had adopted the (to me) blindingly obvious convention of using upper case letters for all multipliers >1, not just M upwards, so kilo would be K, hecto H and deca D.

JohnW2 · 3 Jun 2015

ban-all-sheds said:
And that would be unnecessary and deci-/deca- confusion removed if they had adopted the (to me) blindingly obvious convention of using upper case letters for all multipliers >1, not just M upwards, so kilo would be K, hecto H and deca D.

I can't disagree with that, and have never understood why what you suggest (which I agree seems to be 'blindingly obvious') was not what 'they'adopted.

The fact that such is what most people expect is illustrated by how often one sees ('incorrect') "K".

Kind Regards, John

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test a capacitor

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