Moderators: Random Orbital Bob, nev, CHJ, Noel, Charley

 Reply
User avatar
By pollys13
#1295612
A machine with this specification:
Voltage 1 phase + N + Earth 230V /50/60 Hz
Motor rating 1.5Kw
Motor full load current in amps 1 PH 9.0A
Starting current in amps 1 PH 56.0A
Required fuse size in amps 1 PH 25A
Required cable size 1PH 2.5mm
Can one use some type of phase, invertor, stepper transformer to run the machine safely off a 230 volt domestic supply?
By lurker
#1295620
Unless I am missing something, it's just plug and go off a normal 3 pin plug.

Edit: just spotted the required fuse size. Seems a big start surge to me?
By sunnybob
#1295626
Thats a heavy motor! Exactly what is it running?
Your problem is whats known as "start up voltage" which is the "kick" the motor needs to start turning.
This can be overcome with capacitors and accommodated with slow burn fuses, but its not the way it should be done.

The correct way is to have a dedicated cable from your consumer unit, with a 32 amp MCB and a wall terminal with a cooker type socket for it to be hard wired in.

Always consult a local electrician in unusual circumstances.
(or read the instructions of course :lol: :lol: )
User avatar
By Trevanion
#1295656
No electrician, but a single-phase PT255 with a 1.5KW motor should borderline run off a regular 13A plug as I've seen many with a regular 13A plug on, but really they should have a 16A OR 32A plug on or be wired direct.

I think the numbers in the newer manuals is buttocks-covering more than anything. "Did you wire it properly into a supply exceeding 25A? Then that's your problem" etc... I've got a couple of 2.2KW machines that run fine off a 16A plug and a couple of 1.5KW machines that run fine off a regular 13A house plug, never been an issue.

So long as you're quoting the right information of course and haven't picked up the single-phase specifications by accident when you meant to post the three-phase spec.
By sunnybob
#1295668
The other problem here is the length of cable involved. If this is in a shed at the bottom of the garden running off an extension lead, its going to trip the fuse every single time.
If the consumer unit isnt in the same building its not going to work off a 13 amp supply.
By ManowarDave
#1295669
Hi,

As sunnybob said, you should install to a separate MCB on the consumer unit. Make sure it is a type D (also known as d curve). These are designed for loads with high in rush current such as motors.

From consumer unit to double pole isolator then 16A (blue) socket.

Dave
By sunnybob
#1295671
Dave, as you say, a blue socket single phase is 16 amp.
The spec requires a 25 amp fuse. That would lead to overheating of the plug / socket over time.
hard wired would be best case.
By ManowarDave
#1295680
Hi sonny,

Agreed on hard wired. Missed the 25A fuse rating. However given the characteristics of the type D MCBs and the continuous current rating of the motor, I'd put it on a 16A MCB.

Dave
User avatar
By pollys13
#1295691
Trevanion - yes was correct spec for a single phase machine, manual does say not to run on a 13 amp socket.

sunnybob - The correct way is to have a dedicated cable from your consumer unit, with a 32 amp MCB and a wall terminal with a cooker type socket for it to be hard wired in.
Yes I'll go down that route, wouldn't want something to go pear shaped, then trouble with the insurance man :)
Thanks everyone else for chipping in..... sorry :)
User avatar
By Trevanion
#1295712
After having a think about it I realised why there’s such a large start amperage specified, there’s two motors in the machine which I had totally overlooked and forgotten about. There’s the 1.5kw cutterblock motor but there’s also the motor for the powerfeed. Which if memory serves is about 0.5kw. But I believe on the single-phase machines they’re on separate switches so it’s not one massive power drain trying to start two motors at the same time from the same supply.
By Sideways
#1295718
PT255 - the little 10" wide one, is a single motor unit. Feed rollers are continuously driven from the spindle drive via a flat belt and spring loaded pulley before you get to the chain drive.
PT's have a fair weight to spin up in the block and feed rollers so no surprise that the startup surge runs towards the higher end: 6-7x full load current. I've metered the startup on a similar size axminster trade machine and they pull 50 odd amps for a couple of seconds too before dropping back to about 7A at idle.
I'm absolutely not saying that you should, but a machine of this size will run off a 13A plug. It is also so close to the limit of a 13A fuse that it ages them and you could be replacing the fuse every few weeks.
Admittedly not having done the time / current / heating calcs but for a full load current of 9A, I would expect a relatively small machine like this to run fine off a 16A circuit wired in 4mm to a type C MCB.
I bought one. That's what I plugged it into. It ran fine, but the motor was worn so it's part stripped pending a refurb. I didn't bother doing any further measurements.
The machine is protected by a thermal overload relay in it's starter. It will take no harm from being plugged into a higher capacity circuit than it needs.