Haverhill welder/generator problems

[Pennine Ploughing]

I have a Haverhill welder gen, like this one below

now once you start to use power, the engine is running fine, but the volts drop off to nothing,
and same with welding, every thing running fine, soon as you strike an ark, again the power drops off to nothing, but the engine is still running as it should, and it dont kick in and drag the engine down a little to kick the govener in and pull hard,

i think it might be the condencer, its looks like a 40mm round by 80mm tall and 2 wires to it,
would i be right?

TIA john

 

[El arado]

Could be the cap', but why do you think so. Best check all connections, usually generators have an "exciter card" which basically kick starts the output. Look for corroded connections etc., if the windings look good then it will be a cheap repair, check out RS Components for spares, they aren't the cheapest but they carry the stock. Haverhill have been around for years, and are reliable machines.

 

[TheTallGuy]

Sounds like it's a problem with the avr/exciter - obvious culprit would be the brushes, but may well the avr card or field winding.

 

[Pennine Ploughing]

it had new brushes about 6 months ago, and they are ok

 

[TheTallGuy]

it had new brushes about 6 months ago, and they are ok

I'm not familiar with the Haverhill units - is it electric or manual start?

 

[Pennine Ploughing]

I'm not familiar with the Haverhill units - is it electric or manual start?

it is fitted with both

 

[El arado]

Can you see the writing on the Condenser? It will probably the same type as a single phase motor start cap', and they are cheap.

 

[Pennine Ploughing]

yes just 2 wires to it

 

[El arado]

Can you see the voltage rating and the µF rating?

 

[Pennine Ploughing]

uF rating is 35 +-5%
MKA 35 -450
Un 400 V ac B
Un 450 V ac C
28/85/24 PO 50 Hz

is that any good, thats whats on it

thanks john

 

[TheTallGuy]

Something like this should be equivalent...
http://uk.rs-online.com/web/p/polypropylene-film-capacitors/3779147/
It's probably the cheaper/easier thing to try first.

 

[Pennine Ploughing]

thanks for that looks like it might do,

 

[El arado]

Its a std run cap' - could be the problem. Do you have a single phase motor with a similar value cap - try it. Plenty on Ebay, http://www.ebay.co.uk/sch/i.html?ad...=0&_nkw=35uf+450+capacitor&rt=nc&LH_PrefLoc=1
New brushes fitted, were the slip rings clean and in good condition.
I assume the motor runs up to full speed.

 

[Pennine Ploughing]

yes slip rings cleaned in the lathe when new brushes where fitted,
motor running at full speed
i will get a new cap this next week and try it

many thanks john

 

[Mursal]

If you have all the easy stuff done and you have voltage before you load it? Then probably, Automatic Voltage Control (AVR) as already mentioned. Just a few click

 

[Pennine Ploughing]

Thanks for the help, will try sorting it when got time