Looking for 250W 4 pole motor.

[richardandtracyParticipant @richardandtracy]

I was helping clearing out part of the workshop at work last week, and one of the tools that was destined to be skipped was an industrial scroll saw for wood or sheet metal. It has sat on a shelf unused for 15 years. It has a 3 phase motor, but the plug has been cut off – the machine is old enough for the insulation to possibly have broken down. Anyway, instead of skipping it, it found its way into my workshop (all 80kg… not easy even with my wife helping).

However, I don't have 3 phase at home, so need a 1.3hp/ 250 W motor for it, and it'll have to be a 4 pole motor to nearly match the original speed. I've had a quick look at Machine Mart motors, and after pushing my eyeballs back in, I thought I'd ask those who know more about better (I really mean cheaper) places to get a motor. Can you recommend me somewhere?

Another question I need to ask is: Does it need a starter? The Machine Mart motors are only warranted if you use a soft starter. Is it needed, or are they being a bit prissy. I'm not sure I can see any sort of starter on my Warco lathe, but then, I'm not very electronically minded.

Regards,

Richard.

[richardandtracyParticipant @richardandtracy]

Does it need a starter?

[Keith LongParticipant @keithlong89920]

Richard

I hate to say it but I think if you're looking for a new motor then Machine Mart are at the cheap end of whats available. A trawl round EBay will produce very similar prices.

Machine Mart don't actually say use a "soft start" but specify a starter with "full overload protection" and then tell you which page to find them on. The starters there are what are referred to as DOL starters (direct on line) and have overload cutout built in – you choose the starter according to the full load current of your motor.

If you want motors much cheaper than Machine Mart you'll be looking at secondhand.

Keith

[richardandtracyParticipant @richardandtracy]

Ho hum.

Thanks for that Keith, even though it's not what I wanted to hear, and Machine Mart's a fair bit more than I had mentally budgeted for. It means that this 'free' machine will cost me as much as a DIY scroll saw. However, the quality will be much greater.

Regards,

Richard

[LambtonParticipant @lambton]

Richard,

It is always advisable to fit a proper motor starter as this will provide two advantages:

1. Overload protection by cutting off the power to the motor if the current rises above a safe level (for the motor) Overloads are adjustable within limits so it is essential to get one covering the correct range for your motor.
2. The starter will give a "no volt release" function meaning that the motor will not re-start automatically if the power fails and then comes back on again. The motor will always have to be started bu manually pushing the start button.

Machine Mart will only guarantee their motor if it is fitted with a proper starter (not a soft starter) as this will ensure the motor has not failed through being overloaded beyond its design limits which is possible if connected directly to the supply. This is a reasonable condition to apply.

Eric

[Les Jones 1Participant @lesjones1]

Hi Richard,
If you find a 1.3hp/ 250 W motor let me know. It could be used to make a perpetual motion machine.

Now being serious, from the weight of the machine I would think 1.3 HP would be about right but it seems a strange number. 1.5 HP would be more normal but that would be about 1200 watts. If the motor is 250 watts it would be about 0.3 HP which seems a bit small but would fit if you misread 0.3 as 1.3 on the motor plate. You will need to confirm the rating before ordering a motor.

Les.

[Billy MillsParticipant @billymills]

Les

if you read 1/3 HP, 250W makes sense. That would be plenty for a fretsaw blade ( it is only one arm power after all).

 

Billy.

Edited By Billy Mills on 13/03/2014 18:08:57

[Les Jones 1Participant @lesjones1]

Hi Billy,
Yes you are right. For some reason I was thinking of a bandsaw. Also I think a marking of 1/3 HP is more normal than my suggestion of 0.3 HP.

Les.

[Keith LongParticipant @keithlong89920]

Has anyone tried the schemes in Jim Cox's books "Electric Motors" and "Electric Motors in the Home Workshop", where he shows a 3 phase motor running on single phase with a bit of fairly simple re-wiring and a handful of external components. Could be a solution for Richard?

Keith

[RobboParticipant @robbo]

Keith,

The usual method of running 3-phase on single phase by using a capacitor etc to create a false 3rd phase loses power from the motor, and if it starts out at 1/3 HP I would think it needs to keep at that.

Richard,

If the original motor was a 1/3 HP 3-phase, then I would use more power in single phase, say 1/2 HP.

[John Stevenson 1Participant @johnstevenson1]

Got a 1/4 Hp single phase one here.

It's brand new but been fitted in error as it should have been a 2 pole. 11mm shaft size, flange mont, no feet but has the tapped holes for them.

Any good ? Only looking for beer vouchers for it but carriage is going to be about £8.00 ?

[richardandtracyParticipant @richardandtracy]

I do apologise, I had a tripe writing error. It is of course 1/3 hp not 1.3 hp.

PM sent to John S.

I have the Lindsay booklet on running 3 phase motors on single phase, but the motor is so old I really don't trust the insulation in it. The 3 phase plug had been cut off, and that usually happens at my work place when it's electrically unsafe. By the look of the font on the nameplate, and motor housing shape, I suspect the scroll saw dates back to the 1950's, as the cooling holes, casing shape and styling are similar in general style to my dad's 1950's Wolf electric drill. The saw has done a lot of work, one of the guys in the woodwork department joined the company in the 1970's as a lad, and can remember the saw being used almost all day long cutting apertures in plywood – but can't remember when it stopped being used.

Regards,

Richard.

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