[img]
[/img]
I have been offered a 200 litre compressor at a good price as it requires 3 phase power. Would it be possible to remove the 3 phase motor and attach a single phase. the motor on the compressor is 5.5 HP.
From memory, I think the biggest motor you can reasonably run on single phase is 3hp. You could of course run two motors (stagger the starts to avoid
tripping ?) or use a 3ph motor (and change the pulleys/ratio - if it's too much hard work for the motor)
It maybe that it'll just take a bit longer to fill but the cfm will be down.
Not worth the hassle though really.
Ditto, think 5.5Hp is too much for single phase.
As at your local electric motor specialist.
3hp is not the limit for single phase - many showers are 8-10KW (0.75KW = 1hp approx)
3hp is the just below limit for running off a 3 pin plug (13amp x 235volts = approx 3KW = 4hp)
If you uses a 5.5hp single phase motor you would need something like a cooker socket and wiring. I am spending the day fighting with the wiring of my
Partners 7.5KW kiln located in her shed at the bottom of the garden. I have needed huge cable etc but it works ok. I have had to upgrade the cable to
12mm2.
I would suggest that you keep the existing motor and use a phase converter - 3 phase motors run so much better.
I was thinking about a 3hp motor running from a 16amp plug & socket or hard wired. my main concern is will a 3 hp motor shift a 20cfm compressor pump ?
I replaced the3 phase 3hp motor on my two post lift with a single phase 4hp motor, it has no problem and the initial start is very hard when loaded with a car, it cost just under £200
Motors also take a LOT more current for a brief period during startup
I have just replaced my compressor with a much bigger older belt drive unit
The Brook Crompton motor on it states 12.5 amp (so I would assume its circa 3 hp)
Not sure if this is surge or when its running
Interestingly the motor has grease nipples at the front and back and also has a 3 phaze rating on it as well as the single phaze on it's plate
It was tripping the garages 16a MCB and I replaced it for a type c motor rated MCB
It now makes the garage flourescent lights dim and flicker when it runs :-(
(but at least it does run and is a shed load quieter than the direct drive unit that I had)
Can't recall what size wire I used to feed the garage but may need to go up a size
Regards
Rob
quote:
Originally posted by dave
I was thinking about a 3hp motor running from a 16amp plug & socket or hard wired. my main concern is will a 3 hp motor shift a 20cfm compressor pump ?
quote:
Originally posted by Litemoth
quote:
Originally posted by dave
I was thinking about a 3hp motor running from a 16amp plug & socket or hard wired. my main concern is will a 3 hp motor shift a 20cfm compressor pump ?
Yes but you may have to change the pulleys to change the ratio to take some of the load off. If it's a big piston pump then it'll struggle to start. The 'cost' of this conversion will be that the cfm will be lower of course.
A 3ph 5.5hp motor is a powerful unit and isn't going to be replaced by a single phase 3 - 4hp unit
I think a single phase 3hp draws about 17A and a 5hp will be around 28A but during startup it will be significantly more than this depending on pump resistance.
A replacement motor above 3hp will cost quite a bit as will a inverter to drive the motor you have.
In my humble...Unless you use a lot of air, a modern vee-twin 14cfm pump matched with a 3hp motor is a good economic choice....on a 50litre or 200litre tank.
quote:
Originally posted by daviep
Maybe want to check your maths?
3hp = 2.25Kw which would pull 9.4amps at 240v
5hp = 3.75Kw which would pull 15.6amps at 240v
Cheers
Davie
Assuming an induction motor, the start-up current is anywhere between 6 and 10 times the running current. It only lasts a short while though. Appropriately rated fuses or breakers withstand the extra load for long enough and the cables don't have time to become overheated.
quote:
Originally posted by daviep
quote:
Originally posted by Litemoth
quote:
Originally posted by dave
I was thinking about a 3hp motor running from a 16amp plug & socket or hard wired. my main concern is will a 3 hp motor shift a 20cfm compressor pump ?
Yes but you may have to change the pulleys to change the ratio to take some of the load off. If it's a big piston pump then it'll struggle to start. The 'cost' of this conversion will be that the cfm will be lower of course.
A 3ph 5.5hp motor is a powerful unit and isn't going to be replaced by a single phase 3 - 4hp unit
I think a single phase 3hp draws about 17A and a 5hp will be around 28A but during startup it will be significantly more than this depending on pump resistance.
A replacement motor above 3hp will cost quite a bit as will a inverter to drive the motor you have.
In my humble...Unless you use a lot of air, a modern vee-twin 14cfm pump matched with a 3hp motor is a good economic choice....on a 50litre or 200litre tank.
Maybe want to check your maths?
3hp = 2.25Kw which would pull 9.4amps at 240v
5hp = 3.75Kw which would pull 15.6amps at 240v
Cheers
Davie
My 4hp tripped a 16 amp MCD on startup, moved to 32amp which resolved things.
My consumer unit is in the garage, 6' away from the motor, it does make the house lights flicker.
Problem solved
[img]
[/img]
quote:
Originally posted by dave
I was thinking about a 3hp motor running from a 16amp plug & socket or hard wired. my main concern is will a 3 hp motor shift a 20cfm compressor pump ?