3 phase

[bob_c]

Hi, i know very little about machine electrics or electrics full stop!
Ive been offered a decent bandsaw cheap(all cheap ones seem to be 3 phase) but its 3 phase and i only have normal 13 amp 240v household supply.
Is there a cheap way of operating this saw.Rotary converters seem expensive,does any one know about these digital converters/inverters which seem cheaper on ebay.
Also is there more involved than just purchasing these digital ones.Extras i should know about /need?

 

[OllyK]

I have considered invertors etc and certainly 3 phase should give smoother running and more power. However, it is also worth considering looking for a suitable 1 phase 240V motor and swapping it over then flogging the motor on eBay.

If you're creative you can also user a 3 phase motor to act as a 3 phase generator. There is infon on this on the web, not sure how effective it is though.

 

[bob_c]

Hi Ollyk thanks for the reply.The deal on the bandsaw is 1/3 of the retail price and includes an extractor.The saw is almost new as well.
Im afraid ive never swapped a motor and wouldnt know where to start,which is why i need it explained in simple terms :?
I usually just buy machines and plug them in ,i,ve never messed with the electrics on them.
How are these inverters /converters used or wired in,do you need different switch gear/starters ,etc...

 

[OllyK]

Hi Ollyk thanks for the reply.The deal on the bandsaw is 1/3 of the retail price and includes an extractor.The saw is almost new as well.
Im afraid ive never swapped a motor and wouldnt know where to start,which is why i need it explained in simple terms :?
I usually just buy machines and plug them in ,i,ve never messed with the electrics on them.
How are these inverters /converters used or wired in,do you need different switch gear/starters ,etc...

I suspect you'll need the services of an electrician if you go the invertor route. From what I have seen, most have a standard 240v supply, probably wired back to it's own breaker on the MCB. The machinery is then hardwired in to the invertor or on occasion may be done via a 3 phase plug, usually red with 5 pins in it, but looks similar to the 100v yellow jobs.

Swapping a motor could be easier depending on how easily you can get one with a suitable mounting )or how easily you can cobble something up) assuming it's a pulley system. If it's direct drive then it becomes more complicated.

HTH

 

[Argus]

.

If you want to run it on single phase, you've omitted the most important detail - the capacity of the original motor, which you will need to at least match, or better, exceed in a single phase version.

As a practical guide, a domestic ring-main outlet will limit you to a maximum motor size of about 2.5kW.

If it's suitable, you may consider getting the original motor re-wound as a single phase version, but I expect that it's 3 phase for a reason - it's probably too big for a single supply ......

.

 

[bob_c]

Thanks for the replies:

The bandsaw is the Jet JWBS 18 if that helps i think its rated at 2.2 kw in 415v.

 

[bob_c]

Ok ,does anyone know this bandsaw and anyone suggest a suitable quality 240v motor?

 

[9fingers]

I see that rather curiously according to Axminster, this saw is fitted with 1400W (2hp) single phase motor or a 2200w (3hp) 3 phase motor.

This is most unusual as normally the motor power would be the same or even perhaps slightly less for the 3 phase option than the single phase.

The motor rating are corroborated by the Jet website so I assume it must be correct.

As others have said, sticking with 3 phase, you will not only need an inverter but also a 16, maybe 20 amp supply ie more than a standard 13 amp socket.

If you choose to fit the 2hp single phase motor then this can be run from a 13 amp socket.

IMHO the versatility of an inverter which will give you variable speed which might allow metal cutting blade speeds, certainly for aluminium is desirable.

Wiring an inverter is not difficult but from the level of your questions, would be possibly best left to a friend with some electrical knowledge.

Your best source of either inverters or single phase motors is ebay.

Important parameters when buying the motor are the mountings (flange or foot, some have both mountings), the height of the shaft above the mounting foot and the diameter of the shaft. Modern motors tend to be pretty standard in these latter two ways for a given power. Make sure you get the right speed. Common ones will be 1425 rpm or 2850 rpm

The Jet is a very good saw and you should not be put off by these motor issues as once they are solved you are bound to be pleased with the result.

Go for it!

Bob

 

[CHJ]

If you intend to go the convertor route to drive the 3ph motor, first check that your motor is capable of being connected in Delta configuration for 230 volt 3ph operation, most motors have this facility but not all.

(3ph 415volt is Star connected in 'standard' motors. )

Beware of ebay invertors purporting to be capable of running a 415 volt 3ph motors off 240volt 1ph supply, these do not normally carry the CE mark and are I believe derated 415volt 3ph units that have been reworked since original manufacture, the problem being that they can produce large levels of harmonic distortion back into the supply system and you could be unpopular with your electricity supplier if complaints end up at your door.

 

[dickm]

I see that rather curiously according to Axminster, this saw is fitted with 1400W (2hp) single phase motor or a 2200w (3hp) 3 phase motor.

This is most unusual as normally the motor power would be the same or even perhaps slightly less for the 3 phase option than the single phase.

If you choose to fit the 2hp single phase motor then this can usually be run from a 13 amp socket.

Your best source of either inverters or single phase motors is ebay.

Important parameters when buying the motor are the mountings (flange or foot, some have both mountings), the height of the shaft above the mounting foot and the diameter of the shaft. Modern motors tend to be pretty standard in these latter two ways for a given power. Make sure you get the right speed. Common ones will be 1425 rpm or 2850 rpm

Bob

I'd be loth to go the invertor route. The variable speed benefits on a bandsaw are not, in my opinion, likely to be great, and the other problem with larger invertors is sealing against dust.

I went the single phase route on my Startrite 352, and the other point to remember in addition to Bob's (9Fs) ones is that you will also need a new start/overload switch, as the lower voltage single phase motor will take around twice the full load current.
I'd also recommend local motor rewind folk for motors - they sometimes have uncollected repairs. Or your local free-ad paper.

 

[Anonymous]

Bob

I have worked with 3 phase all my working life (25+ years) and would forget the inverter route and swap out the motor for a single phase. Easy to do once a motor of the same frame size is sourced (maybe Axminster as they sell 1 and 3 phase variants?)

 

[9fingers]

Bob

I have worked with 3 phase all my working life (25+ years) and would forget the inverter route and swap out the motor for a single phase. Easy to do once a motor of the same frame size is sourced (maybe Axminster as they sell 1 and 3 phase variants?)

I guess it is just down to personal preferences. I'd use 3 phase everytime and I dont have a three phase supply to the home.
I've even got variable speed on Barry's cyclone so I can reduce the noise level for less demanding dust collecting jobs.
My Startrite 18-s-1 bandsaw designed for wood alone now (with the correct blade) can cut 6mm steel with ease when used with an inverter.

Also you can get better starting torque from a 3 phase motor with or without and inverter. You get No Volt release automatically as well as overload protection from an inverter. Finally the starting surge that single phase motor have can often pop fuses where as the soft start from inverters prevents this.

Just my 2p

Bob

 

[Digit]

I have to agree with Bob, and for the same reasons. A motor swap is pretty straight forward.

Roy.

 

[bob_c]

Thanks to all who`ve replied im still in two minds over which way to go,each way seems to have its own supporters.
A couple of questions though the ebay converters/or inverters as they are called,they seem to be from reputable places who have a seperate website .
Also the axminster catalogue recommends a 20 amp supply with the jet single phase saw,so i assume that would mean upgrading the supply to my workshop?

 

[Digit]

Bob C, let's see if this helps you.
Three phase power is preferred as having more torque, (turning power). which is why machines that are offered with either single or 3 phase motors often have lower 3 phase HP ratings than their single phase brothers.
IMO converters are a pain, depending on the converter's efficiency you might still need a 20amp supply to the converter anyway.
As to whether you need to upgrade the supply to your shop depends on the supply cable's size.
Anything over 2.5 mm should suffice if your supply cable is not over long.

Roy.

 

[CHJ]

......A couple of questions though the ebay converters/or inverters as they are called,they seem to be from reputable places who have a seperate website .
......

Bob, if they are "from reputable places who have a separate website" and designed to run a 3Ph motor at 230volts then they will be fine, my comments above were just to make people aware that there are some rogue ones offered at times, it is not illegal to sell them as long as they do not carry the CE mark, the person using them in a piece of equipment becomes responsible for the requirement to get them certified. The most modified units are I believe manufactured by Teco in Taiwan.

Tonys' 'change motor to 1ph' may well be your best and cheapest option though. Two criteria need addressing, speed of motor, (2 or 4 pole) and shaft size.

Have you enquired of Axminster what price a replacement Iph spare is for the machine?

 

[r896neo]

I looked at similar options recently and I would add that an invertor for a machine like that is going to cost a fortune! For start up power of 4/5 hp im sure you'd be looking near £700

 

[bob_c]

Well sorry to bring this up again.I received my Jet jwbs-18 today by pallet.Boy it was a pain to get it into the workshop ,it was delivered on two pallets one on top of the other ,so it was already a foot off the ground.I bought one of those mobile base`s from axminster after around an hour managed to get it onto the base,then wheel it about twenty yards from the pavement to the workshop.(i dont have a drive, steps and more steps)Then i had to get the 6 ft bandsaw through the 5ft 5" door.In the process ive bent the height raising/lowering wheel shaft(is it easily straightened?)

Heres a pic of the bandsaw and the axminster wv2 extractor in situ at the college in Glasgow it was removed from.I didnt realise the extractor was the more expensive one.Not a bad deal £400 for both including delivery.


Now i have to deal with the three phase problem.Ive decided to go the single phase replacement motor route. Most motors ive seen seem to have a mounting on the bottom not the end.Ive had a price of £200with delivery from Axminster for a replacemnt Jet single phase motor. Looks to be about twice the price of similar generic rated motors.Heres apic of the ratings on the motor.

Can anybody explain to me what all the switch gear is thats on it now.I assume its going to have to all come off to change to single phase???
In this picture theres a big red button with a key,is this an NVR??

JUst above it is two switches i assume are on /off(red and green)

On the other side is this thing with some sort of foot peddle attached and a three phase socket.Is this a on /off peddle or a brake??

Any clarification greatly appreciated!!! :?

 

[Digit]

Some of it I can answer. The single red button is the emergency STOP button. Normally these stay locked into the OFF position once operated and have to be released by rotating the knob.
The other two push buttons are the DOL or NVR START/STOP controls.
These will need renewing for 230v operation or the coils changing.
The pedal I pass on.
End mounted motors are much rarer (more expensive) than foot mounted versions, at your quoted price a pro rewind might be a better option.
Pro winders not infrequently have S/H motors for sale as well, also see if you can modify the machine to take a more conventional motor mount, that's what I did on mine.
I went the whole hog and fitted a brush motor and electronic speed control, worth considering for the flexibility.

Roy.

 

[9fingers]

The pedal will be some sort of safety device. Possibly the pedal has to be pressed to start the saw and it stops as soon as you take your foot off.

A 3 phase inverter off ebay will be cheaper than the new motor you have been quoted. It will provide NVR action and give you the speed control that Roy suggests. To me this is the obvious way ahead - maybe I'm biased?

If you are determined to change the motor you need to find the frame size. this is an industry standard. I would guess at 100 frame.

On a foot mount motor, the 100 refers to the height of the shaft above the mounting plane in mm. Roughly this will be a motor 180-190 mm diameter.

Although motors are standard sizes, there are often 2-3 flange sizes. The important dimension is the distance between mounting bolts. Usually expressed as the diameter of the circle on which the bolts lie called the Pitch circle diameter or PCD. you and measure adjacent bolt centres and do the maths to work out the PCD. (multiply by root 2 = 1.414)
Lastly you need the shaft diameter - likely to be 28mm on a 100 frame motor. The key way in the shaft is standard for a given shaft diameter. 8mm in a 28mm shaft. Check to see if there is a bolt down the end of the shaft on the bandsaw. If so then you want a motor with a tapping in the shaft. M10 is the standard thread (17mm A/F hexagon head)

Armed with these dimensions, you can then search out a motor and it should fit- without these parameters you are gambling on a fit.

Shame you are at the other end of the country as I could have offered more practical assistance.

As for that bent shaft, you should be able to bend it back more or less straight but take it gently. loosen the adjustment first so if you do snap it off, then it will be easier to get the end out than if it is dead tight.

Good luck

Bob