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Variable speed drives?

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mrbmcg

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Hi

I am looking to control the speed of a single phase induction motor. I see a lot of variable speed drives, but they always seem to be three phase outputs.

I guess I could use a single phase of the output but that would pretty much only give me a third of the total power output.

Does anybody have experience of such things and can maybe recommend a solution? The motor is 3HP.
 

DaveL

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Hi Bob,

If 2HP would be enough, I could swap your 3HP 1ph motor for a 2HP 3ph one that came on my new old saw, look here, with one of these controllers from Axminster you would be in business.

I am still saving for a new 3HP 1ph motor.
 

mrbmcg

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DaveL":1qda731e said:
Hi Bob,

If 2HP would be enough, I could swap your 3HP 1ph motor for a 2HP 3ph one that came on my new old saw, look here, with one of these controllers from Axminster you would be in business.

I am still saving for a new 3HP 1ph motor.
Hi Dave

Sorry, the motor is fitted to my Felder spindle moulder. I don't really want to tackle fitting another one.

Thanks anyway
 
A

Anonymous

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Hi Bob,

No quick or easy answer unfortunately, if there was most woodworking machines would have them. The standard way to control the speed of a single phase induction motor machine is to replace the motor with a three phase motor. Then you add a box of electronics that converts single phase to three phase with variable frequency to change the speed.

Of course, if you have a 3 phase supply in your workshop you are part way there.

Wulf
 

mrbmcg

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Thanks for that Tony, I phoned one of the companies from the list that are in Glasgow.

They said that the way to vary the speed of a single phase induction motor is to alter the voltage rather than the frequency. He also added that if you do change the speed via the voltage that you run into heat dissipation problems and that in general it should be avoided at all costs, especially on a woodworking machine :?

Three phase motor plus inverter appears to be the only real route to fixing this safely.

I think I might just try to find another solution to this. The actual problem is that I have quite a few expensive router cutters which are only rated for use at 10,000 - 12,000rpm max, but the router spindle for the Felder CF731 runs at a constant 15,000rpm :cry:

Does anybody have a ready reckoner for cutter diameter vs safe working speed?
 

ProShop

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mrbmcg
I thought you might find the following info useful in reference to variable speed on the Felder single phase multi machines. If you know all this already I'll get me coat :D

The 3-phase option is a inverter drive, which is a solid state frequency
drive. It turns single phase power into 3-phase with the ability to vary the
frequency, which allows for variable speed on the motors. The drive produces
true 3-phase power, it is always on and does not drop out like a static
converter would. The Felder machines do not work well or at all with a
static converter drive. The inverter is a great option and you have full
output of the motor as long as the inverter is rated for the load. The
Felder inverter is fully rated for 5 hp loads.

The motor on the single phase inverter system (5 hp) is the same 3-phase
motor as in the 5.5hp 3-phase configuration, on the inverter system the
motor is rated at 5 hp instead of 5.5. The 4 hp single phase is a 4 hp
single phase motor with no inverter, true single phase motor, it is a
similar motor to what the Italian manufactures call their 4.8 hp motor, but
Felder rates it 4 hp.

The inverter provides power all the time, and also gives the nice feature of
a soft start and dynamic braking. You have 5 hp all the time.

The pros of the inverter drive -

Single phase input with 3 phase motors
More power than a single phase motor
Ability to vary the speed of the motors
Silent operation, and easy hookup, just hookup 230 volt single phase to the
machine
Con ­ the inverters are expensive and one is required for each machine, on
the Felder one inverter powers all the motors. If you had separate machines,
each machine would need an inverter drive.
 

mrbmcg

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Thanks John, it is of interest but the problem is thought that it costs well over a £1000. I would probably have went for this option if I was buying the machine new, but mine is second hand.

Either need to forget it or come up with a more creative solution.

Has anybody heard of any devices/attachments which can be used to alter the diameter of a pulley tempoararily? The reason I ask is that 15,000RPM is good enough for the vast majority of the router cutters I have. If I could just increase the diameter of the pulley by whatever temporarily I could slow the cutterhead down to the required 10,000ish RPM

Getting desparate now I think. :cry:

PS my TS4010 went on ebay for £1160. Not too bad, but not as much as I'd hoped. Maybe I was a bit optimistic. Still, it'll be a good saw for somebody :)
 

ProShop

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mrbmcg

Am I right in thinking that you have the router spindle only.

I ask this, as is it viable to just get the spindle moulder cutters you require provided you also have the moulder spindle ?. And perhaps sell your router cutters to fund the transfer so to speak?
Just a thought :)
 

mrbmcg

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Fixit":3fx6sc7l said:
mrbmcg

Am I right in thinking that you have the router spindle only.

I ask this, as is it viable to just get the spindle moulder cutters you require provided you also have the moulder spindle ?. And perhaps sell your router cutters to fund the transfer so to speak?
Just a thought :)
I have both router spindle and 30mm spindle. Problem is that I have approx £500 of biggish router cutters - Locking Mitre, Drawer lock, finger jointer, panel raising set etc etc. I seriously doubt I can replace all that for what I would get second hand for them.

Might just have to bite the bullet though :cry:
 

OLD

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Is there any way to gear the drive down to the speed you require by fitting extra pulleys to existing shafts changing speed with a belt movement perhaps a jockey wheel to take up any slack the sort of work a engineer could do.
 

paisawood

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Bob,

Only just noticed this thread so my response is a bit late.

I have the same problem with the spindle speed on my Felder KF700, and a possible solution which I have been considering is to remove the rings from the table and drop in a variable speed router mounted on a phenolic or aluminium mounting plate milled to fit the aperture. This would be a more cost effective solution than replacing the motors although only certain routers will fit in the aperture.

Full details can be found in the files section of the Felder Owners Group http://finance.groups.yahoo.com/group/felder-woodworking/ and pictures of a machine with an insert plate (and a very nice Incra twinlinear fence) can be seen at http://www.drayton.nildram.co.uk/IncraTwin

Hope this helps.

Regards

David
 

mrbmcg

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OLD":26bjp1tl said:
Is there any way to gear the drive down to the speed you require by fitting extra pulleys to existing shafts changing speed with a belt movement perhaps a jockey wheel to take up any slack the sort of work a engineer could do.
This is what I was considering, I just don't know anyone local that I can trust to do it yet. I want roughly a 20-30% reduction in speed for the larger cutters which means a 20-30% increace in the circumference of the pulley on the router spindle and a corresponding increase in belt length.
 

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