110v transformer for compressor

[Ken WeeksParticipant @kenweeks58536]

I have a Fox 110v Side Stack Air Compressor.

The only information I can find for it refers to a Fox CF2600 Side Stack Air Compressor – 240v 2.5hp 16 Litre,

110v is an unknown quantity to me.

Would a 2.5 hp motor be used with 110v?

What Kva 240v to 110v transformer would I need?

Ken

[Ken WeeksParticipant @kenweeks58536]

Trying to work out what size transformer I need

[jason udallParticipant @jasonudall57142]

Assuming that your compressor is 2.5hp. Even if 110V.

This translates thus.
2.5 hp..= 2.5*746 WATTS…IE.1865 watts
So you would need 2KVA transformer. .

[jason udallParticipant @jasonudall57142]

Just incase…746 is the number of watts to the horse power..hp

Under most ( don’t ask) conditions a watt of “power” equates to a volt-amp of electical power……there are reasons where it might not but in this case we can say they do.

[Alex CollinsParticipant @alexcollins55045]

2 KVA will run the Compressor. Should be no issue there.

Starting it under load (i.e with 1/2 a tank of air) it will probably pop the Trip from time to time.

Motor Load is ~ double at start up.

Can I suggest at least a 3 KVA transformer if you need this to be reliable. ​
Or make sure that the trip is rated for Motors.

[John McNamaraParticipant @johnmcnamara74883]

It is likely a new 240v motor will cost less than a transformer.

Regards
john

[Ian PParticipant @ianp]

If you do go down the transformer route what you need is an 'autotransformer'.

It will be physically smaller than an isolating transformer and significantly cheaper. Basically it only has one winding which is tapped at the appropriate point. Bear in mind it does not isolate the output so insulation rating and earthing requirements need observing.

Ian P

[AjohnwParticipant @ajohnw51620]

There is usually a plate on the motor that will show the current it draws which will be a lot more than 2.5hp suggests from a straight calculation using 746w = 1 hp. To give you some idea the max motor size that can be run on 13amp 240v supply with a normal plug is reckoned to be 3hp, max current draw 13 amps under a full load. As mentioned here as some probably wont believe

**LINK**

Actually if some one did really fully load a motor like that on a UK plug for any length of time the plug or socket would very probably probably overheat. Some motors will take less than that for the same power rating but it's always going to be significantly more.

I'd hazard a guess that a replacement 240v motor will be the best option not just the cheapest.

John

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[Ken WeeksParticipant @kenweeks58536]

Thanks for all the info perhaps I should expand a bit,

The compressor is fitted with a yellow 110v plug so I assume it has run from a yellow site transformer.

The motor does not have any information on it.

It is not intended to run it for long periods, I got hold of it to supply compressed air to run a couple of small steam engines for my grandsons amusement. So fill the tank and run the engines refill as required.

Ken

"Never assume it makes an ass of you and me"

[Gordon WParticipant @gordonw]

You can get a site transformer 240V- 110V for less than £40 that will drive the motor no problem.

[AjohnwParticipant @ajohnw51620]

I'd guess that it has been run on something like this one – if it is 2.5hp.

**LINK**

John

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Edited By John W1 on 10/11/2015 12:02:22

[Ken WeeksParticipant @kenweeks58536]

Thanks for all the help

Ken

[jason udallParticipant @jasonudall57142]

A cheap way…might be hire /borrow such a site transformer…to see if it serves…
Then you will also end up with a yellow transformer for other purposes…
..

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