Compressor motor HP help

[Aaron_]

I'm thinking of buying a compressor with a dead 5.5hp 3 phase motor i want to change it to single but like a few of you have told me the max single i can run is 3hp on 13a will i be able to get it to work, will i need to change the gearing

 

[daleyd]

You will certainly have to alter the gearing.

Once done then it will take longer to fill. Depending how much you have alter the gearing then this may mean it's not much use afterwards, depending what you want to do with it. (If you won't be using it for anything too demanding it may be fine)

Even altering the gearing may not be enough to actually turn the pump over from a standstill.

 

[rtbcomp]

If you fit the same speed motor and keep the gearing the same the motor will give up before the maximum pressure is achieved, so if you lower the gearing (ie reduce the motor pulley size) it'll get up to pressure but CFM will be less than the original configuration gave.

 

[Aaron_]

this is the kiddy http://www.spraydirect.co.uk/acatalog/abac_b5924_200_belt_driven_stationary_compressor.html

am i wasting my time

 

[brightspark]

what u may have to watch is if making the motor pulley smaller is belt slip if u have to go smaller than 3 inch . a 4hp single phase motor would be better

 

[daleyd]

I could be completely wrong as I don't know if there is some other factors that would come into play, but I would take a guess that as it's a 24 cfm pump so if you reduced the gearing by 50% it should still be capable of 12 cfm.

Might be tricky getting the pulley sizes right, esp if reducing the motor pulley size. Too small could cause issues

 

[normspanners]

what you have to ask yourself is why the motor has quit, it is unusual for 3phase units to go down, not unheard of, of course, but they generally have much more starting torgue than single phase, there maybe a fault with the compressor it'self.
It also may be an idea to fit an unloading solenoid valve to the pump to tank line to help with start up also a cap start/ cap run motor will help, rather than just a cap start motor.

 

[Aaron_]

I've been looking on eBay for a good deal for weeks its been driving me mad this was it http://www.ebay.co.uk/itm/282205436645?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT

but iv just found a sealey one for a good price not to far away

 

[normspanners]

what u may have to watch is if making the motor pulley smaller is belt slip if u have to go smaller than 3 inch . a 4hp single phase motor would be better

agree but what you can do is fit an idler, flat pulley as per timing belts on the slack side of the belt to increase the 'wrap' of the smaller pulley.

 

[brightspark]

it will deffo need an unloader pipe fitting from the pressure switch between tank and pump

 

[brightspark]

agree but what you can do is fit an idler, flat pulley as per timing belts on the slack side of the belt to increase the 'wrap' of the smaller pulley.

yes that helps but not always successful I have one on my donkey saw because of belt slip and its still a bit iffy on a good cut .don't know if his comp is twin belt drive or a rather thick wedge belt

 

[normspanners]

I have one on my donkey saw

You Saw ---- many donkeys then ??, is this a magicians trick?

or am I pinning the tail on the wrong end, is it a bit like this

it only uses------ one horse power !!

 

[normspanners]

or this more like

 

[Mee]

You can get the 240V to three phase converters and run a three phase motor from domestic mains power.

 

[brightspark]

You can get the 240V to three phase converters and run a three phase motor from domestic mains power.

they don't like the starting load of a compressor

 

[gt6s]

If I recall correctly, you used to be able to get big compressors with twin single phase motors.

 

[brightspark]

If I recall correctly, you used to be able to get big compressors with twin single phase motors.

yea I got one. 2 pumps and 2x 3hp motors over a grand if u want one mine was 60 quid

 

[the snooper]

suppose you could fit 2 3hp

 

[gt6s]

yea I got one. 2 pumps and 2x 3hp motors over a grand if u want one mine was 60 quid

The ones i am thinking on used the two motors to run the same big pump.

 

[Mee]

You need the correct 3 phase convertor and it eats the start up load.