Compressor Motor advice

stevie1262

Hi All

Just aquired a Compressor, it is a Bristol BP 8V model 3S10-40.
Now it was rarely used and fully serviced but as usual ran off a 3 phase supply......but...where i want to use this we dont have access to 3 phase, so thinking all I had to do was fit an Invertor/Convertor to run this off single phase 240v....but staggered by prices of over £1500 for a Rotary Convertor...or to change the Motor for an equivalent 240v one is over £500

Now my question is what is the best way to get this up and running? after doing the maths an invertor which is cheaper wont really work...and not forking out £1600 for a convertor (that may or may not work!)

It currently has a 5.5Kw Motor, will this work with a smaller Motor - say a 3Kw single phase as you can pick these up at a reasonable price. The other problem is if i went to 5,5Kw single phase it would draw about 30amps which is a helluva lot....any ideas appreciated.

Dont know if its worth keeping or am I ????

stevie1262

...sorry, just read the previous threads with someone running a similar compressor from a single phase 3Kw...any mods needed such as smaller pulley?? ....apart from a 20+ amp supply

also seen these
4hp Single Phase 2-Pole Motor - Single Phase Electric Motors - Machine Mart

any thoughts...i dont mind spending £200 ish but thats it!

what about Petrol/Diesel Engines seen a few on Ebay but what size would work( not bothered about upsetting the neighbours :p)

cheers

Stevie

Numpty diver

Hi Mate, is the motor Green ? does it have a box on top with four screws ?
Some of this motors were built to use 240 or 3 phaze .
open the box .. whats inside?
Dean

Beanie

Honda do a 5.5 HP petrol engine suitable (loads on ebay).

The compressor is likely to be more noisy than the engine, if you have some engineering / welding / fab skills you can make and exhast extension that

1. moves the exhast awway from the inlet
2. lets you run the compressor inside with the exhast out side
3. allows a bit more silencing than the standard exhast

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PeteS

If something takes 5.5kW to drive it, you won't get very far on 3kW! Large single phase electric motors are expensive, inneficient, and need LARGE power supplies!

Three phase motors cannot be made to run on single phase. They may have 240/415 volt windings inside them, but they still need three phases.

I like Beanies suggestion of a 5.5kW petrol engine. Just choose the pulley sizes to suit.

louisrankin

I bought a Bauer Capitano which had a three phase motor on; I just fitted a single phase motor. I think it is even the one you have in the hyper link, just make sure you buy the same shaft size so you can use your old pulley also get a single phase motor that runs at the same rpm. I also fitted a blue 16 amp 240v plug and run it from its own 20amp supply. What size is the compressor? If you fit a slower motor the only affect it will have is it will pump a bit slower.

Louis

Nemo1957

Your most economical change will be a new motor in the short run, however it will cost more to operate. 3 phase motors are more efficent than single phase. Using a lower powered motor will work, howver you may have to put a smaller sheave on the smaller motor to give it enough power (mechanical advantage) to spin the compressor. Naturally the motor will spin at its design RPM but the compressor will be turning slower. This will reduce the output CFM of the compressor making your fill times longer and using more electicity.

When I bought my compressor I went the opposite way you are. I have 3 phase available, so I went to a larger 3 phase motor with a larger sheave and turn the compressor faster. My 5.5 CFM Bauer now puts out 8CFM and I use a great deal less energy doing it.

Mike

G4SSG

Hi steve
don't even think about buying that sort of motor , it won't last a week...
you can occasionally pick up the motor you need s/hand...always physically large and extremely heavy ...invertors as you have found are just too expensive ...i have 2 compressors fitted with old school single phase motors,which were designed for continous duty ! you must find this type for your compressor.they were available up to 10 hp ,but now becoming rare!
5 hp (4 kw )are still about...mine pull about 25 amps under load , so a 13 amp plug top is out of the question...i have pics if it will help you ......martyn

cool_hardware52

1. Change to a large single phase motor. Such motors are expensive, and may require a electrical service larger than you have available. Check this first. Starting load on a 7.5 hp single phase motor is going to be pretty impressive.

2. VFD, or variable frequency drive. Some of these are able to input single phase and output 3 phase. Not cheap, but from an installation stand point a bit easier and cheaper.

3. "Roto Phase" single to three phase converter. Very expensive to purchase and install. Produces true three phase power. Installation is fairly complex.

4. Solid State "Phase a Matic" Uses large Capacitors to create a third phase. Not true 3 phase, and any motor operated from it will "Loose" about 1/3 of the name plate HP (or kw) Not too expensive to purchase, less expensive to install than Roto Phase, a bit more involved than a VFD.
Reduction in name plate output will require changing sheaves.

5. Petrol engine. Costs and complexity vary.

6. Sell Compressor and buy one appropriate for the electrical service type and size you have. 7.5 hp pump should be about 10 cfm. Pretty big for a garage fill station.

If all you are filling is the occasional Rebreather tank the cost of power will be the least of your concerns.

Tobin

stevie1262

Cheers, ...

Looks like Beanies Option is the way to go, a 5.5hp motor is fairly cheap, dont fancy spending vast amounts to find it is a waste of time,

I will be filling mainly 3l's and the occasional 12l's , and yep welding isnt a problem to make an external exhaust...

Any advice on Motors and Pullies appreciated, probably start with the standard one and see what happens

cheers