power and induction

[pike]

I've been running all my tools off 13amp and just realised I should really read up on the do's and don'ts regarding power.

As I understand it, up to 1500W induction motor is ok for 13amp but any higher and I might have to look at 16amp supply.

However, what if I have something with around 2000W but not induction?

If anyone knows of a good online resource which would explain the basics to me I'd appreciate it!

pike

 

[OLD]

Watts= Volts x amps ok for rough calculations .
2000w = 240 x ? so its 8.3amps which is no problem. 3120watts is your max .Note also 1 horse power is 746watts.
Any conversions just put in google.

 

[Tusses]

Watts= Volts x amps ok for rough calculations .
2000w = 240 x ? so its 8.3amps which is no problem. 3120watts is your max .Note also 1 horse power is 746watts.
Any conversions just put in google.

yeah - but that is continuous power

induction loads do strange things ! (otherwise I'd have typed the same answer as you ! )

 

[pike]

The sums are helpful to me thanks! but yeah the second part of the question was what difference induction makes to me working out if I can use 13amp or not?

It sounds to me that if it's induction, I need to stay below 1500W. If it is not induction then I can get away with more.

cheers.
pike

 

[Tusses]

I would have answered - yeah , it'll be fine ... bla bla

but

I have a 16A mig welder running off a 13A fuse. Had it 6 yrs, never blown a fuse.

I just got a 1 1/2 Hp Table Saw and it has blown the 13a plug fuse within a week !

so now I am not so sure .

I will watch this thread and learn

 

[Tusses]

to add - it blew the fuse on switch on , not under load

 

[Raggy]

Starting your machine will draw a lot more than when it is running, my workshop lights go dim for half a second or so when I start my t/s or mitre saw.

 

[harryc]

I have a triton Workcentre with the Triton 200W saw running off a 13A fuse and have never had a problem, I think it varies on house electrics how far the fuse is from the ring main etc etc.

P.S With a limited power supply in my garage I have even had the dust extractor running simultaneously with the Saw off the same fuse.

Harry

 

[OLD]

Looks like i missed your point ,when a motor starts up it can look like a short circuit until it gets moving (movement generates a flux that reduces its current requirement ) so inertia and load come into it .
A practical example my sip saw 2200w (3hp) will start and run on 13amp but only a few times and the fuse blows other peoples are fine so i have a 16amp feed.

 

[Tusses]

Starting your machine will draw a lot more than when it is running, my workshop lights go dim for half a second or so when I start my t/s or mitre saw.

yep - I know that much - thats where I come unstuck with induction ! I dont know how much extra 'umph' it needs to get going. My 3Hp router starts up no problem - but that is brushes

 

[Digit]

The problem with start ups is the inertia of the moving parts. A router cutter will allow a motor to spin up to working speed PDQ. A large diameter saw blade will take longer, and untill the motor is up to speed the current taken will be in excess of the rated current.
So a motor that is starting something large and heavy is more likely to blow a fuse than the same motor starting something small and light.
In tech terms the inrush current tends to infinity, as stated earlier once the motor begins to spin it limits its own current.
So it is not just the motor's rated Wattage you need to consider but the time it takes to come up to speed.

Roy.