test a capacitor

[Harbourwoodwork]

can I test a capacitor ;
300 MFD
125 VAC
with a multi metre?
Cheers Ian

 

[flyingsparks]

You need a multi meter which can measure capacitance. Most simple meters only go up to 100MF I believe.
Is this a start cap from a single phase motor?

 

[Harbourwoodwork]

Yes you are right about the use of the cap,it of a surface planer.
my multi metre has 20 uF position is that any use .?
Cheers Ian

 

[333rocky333]

uf is mfd
micro farad
( think its lower case)

So 20 is too low

I think there is other ways to test and some are on youtube, whether they work I dont know

 

[JohnW2]

So 20 is too low

It is, if the OP is interested in measuring its capacitance. He could start by using the resistance range of his meter. It will initially indicate very low resistance, as the cap charges up, but should then gradually rise. If it remains low for a long time, even with the low voltage a multimeter, then he's very probably got a dead capacitor.

Kind Regards, John

 

[conny]

What is actually happening with your planer?

This could help pinpoint if you are looking in the right area to solve the problem.

If it is refusing to start, even though there is an electrical supply to it, the capacitor is one of the first things to check.

 

[JohnW2]

If it is refusing to start, even though there is an electrical supply to it, the capacitor is one of the first things to check.

Indeed - that could well be why the OP is checking the capacitor

Kind Regards, John

 

[Harbourwoodwork]

I am trying to sort out a problem on the machine
It keeps tripping the main fuse on start up ,I was advised to check the cap by the seller Axminster.
Cheers Ian

 

[flyingsparks]

Has it been ok on this supply? What is the rating of your 'fuse' it is tripping? Is it a fuse or a mcb?
Motors take a large inrush current which will trip a B type mcb, if this is what is tripping. A C type may solve your problem, but certain checks need to be done first to make sure it is safe to fit one.

 

[Harbourwoodwork]

The main breaker in my workshop trips and the main breaker in the fuse box before that also trips I think thats three phase 100 amp box
Cheers Ian

 

[flyingsparks]

Can you take a photo of the items which trip and post it here?
Or if not can you see what markings are on it, it should say something like B20 or something similar.
What is the rating of the motor?

 

[333rocky333]

Hi Dave hows it going?

motor spec;240 V
current 5 A
H P 1
RPM 4500
The motor is quite big 6 1/4" Dia

The main RCCB in the workshop trips,
80 AMP
Tripping current 30mA

The main breaker further back down the line also trips;
RCCB 100 A 300 mA
18R 100/300/4

Cheers Ian

A basic test worth doing with your multimeter,
Unplug the unit if it is on a plug and measure resistance at plug.
L to E
N to E
Though if the motor has a double pole starter you may get misleading readings

 

[winston1]

uf is mfd
micro farad
( think its lower case)

No it is not uF, it is µF. (Greek letter µ).

 

[333rocky333]

uf is mfd
micro farad
( think its lower case)

No it is not uF, it is µF. (Greek letter µ).

I know that.

my multi metre has 20 uF position

I think hes more interested in getting the planer sorted than a minor detail obviously due to the lack of the μ on his keyboard.

 

[RF Lighting]

Finally winston posts something factually correct, but true to form it's of no help to anyone