5.5Kw 3ph motor off a single ph supply

[difflock]

Looking at buying an electric firewood saw, I tried a single ph powered one a good no of years ago, and rather opted for the PTO version.

But, man o man an electric saw would be so handy for working in the shed.

But if I want more "oomph" I gotta go 3ph, so I need a ph convertor.

I seem to remember our single ph supply was stated to be good for 8KVA/8KW

Any advice would be gratefully received.

marcus

[topchippyles]

I have a 5.5 hp 3 phase converter i no longer use as i upgraded to a 15 HP one because i have bigger machines in my workshop if your interested.

[Conor Wright]

I picked up a Clarke converter from wholesale welding supplies, max 4kva if I remember correctly.. runs my planer and circular saw with ease. Not big money either.

if you know a good electrician, they should be able make up one for you?

[Squaredy]

I have for years run a 5 hp saw from single phase supply.  It was on its own MCB from the dist board but luckily the saw was very near.  How much HP do you need, and what type of saw?  

[difflock]

Squaredy,

Are you saying you ran a 5HP single phase motor?

I can understand the need to be v close, or use a shocking heavy power lead if that was the case.

Not bought a saw yet, but looking at a few the 3ph ones seem to be 5.5 or 7.5kW

So to round up the 5.5KW=7.5HP.

Also considering the electric saw option for the Logosol mill, which would be 3PH, and if the same ph converter could drive either  .  .  .

marcus

[Squaredy]

1 hour ago, difflock said:

Squaredy,

Are you saying you ran a 5HP single phase motor?

I can understand the need to be v close, or use a shocking heavy power lead if that was the case.

Not bought a saw yet, but looking at a few the 3ph ones seem to be 5.5 or 7.5kW

So to round up the 5.5KW=7.5HP.

Also considering the electric saw option for the Logosol mill, which would be 3PH, and if the same ph converter could drive either  .  .  .

marcus

Yes it was a three phase machine that I wanted to run on the mains so I converted it by swapping the original motor for a single phase one.  It worked great and I only retired it in Jan due to the rest of the machine being knackered.  

 

The frustrating thing is that a motor like this uses no more power than an electric kettle once running.  It is the startup that is the killer.

[difflock]

I cannot understand, that with modern electronics, that it should be beyond the ken o man, to cunningly arrange super-capacitors, to provide for the necessary start-up current, without overloading the incoming supply. 

And fine if it only allows a start every 30 mins/1 hr whatever, no odds, for the vast majority of users.

By the way I read an article about single phase motor development in the USA, that using, if I understood half correctly, a beefed up version of the technology used in brushless DC cordless power tools, they can run 100HP motors on single phase.

WOW!

Marcus

 

[Dan Maynard]

An inverter driving a three phase motor from a single phase source will give you the soft start you desire. In round numbers you need 4A of single phase per kW (think 250volts to make the maths easy) so electric heaters are limited to about 3kW on a plug, will be something over 20A for 5kW so you probably want a 32A socket installing with cable straight back to fuse board.

[Conor Wright]

2 minutes ago, difflock said:

I cannot understand, that with modern electronics, that it should be beyond the ken o man, to cunningly arrange super-capacitors, to provide for the necessary start-up current, without overloading the incoming supply. 

And fine if it only allows a start every 30 mins/1 hr whatever, no odds, for the vast majority of users.

By the way I read an article about single phase motor development in the USA, that using, if I understood half correctly, a beefed up version of the technology used in brushless DC cordless power tools, they can run 100HP motors on single phase.

WOW!

Marcus

 

They already do that with large motors being run on generators. Not sure how though, seen a big old sawmill coming to life on a phased start-up, impressive stuff.. It came up to speed over about a minute, but it put the gennie into full Volkswagen mode, black smoke a fiat 11090 would be unable to achieve! Once up and running there was no sign of pressure on it.

[djbobbins]

I’m not a sparky, but maybe something like this...

https://uk.rs-online.com/web/p/soft-starts/1756257/