Induction motor vs older style?

[petro1headParticipant @petro1head]

Been looking at pilar drills and notice they are advertised with an induction motor.

Are induction motors new to drills etc and what's the difference between these and older style motors?

Also I notice that SIP now sell a variable speed drill, this has no belts so will this be an induction motor or something different.  I has always assumed variable speed motors were 3 phase with an inverter?

Edited By petro1head on 12/03/2017 17:32:53

[petro1headParticipant @petro1head]

[Clive FosterParticipant @clivefoster55965]

Induction motor is the older style, whether single or three phase. The real deal, if decently made capable of running for many years with minimal or no attention. Inherently single speed so needs belts, gears or other form of speed changing drive to cover a wide range of drill sizes. Belt or gear drive means proper step up in torque to cope with larger drills.

Non induction in this context usually means DC motor with electronic speed control to cover the needs of different drill sizes. Power drops off with revs so less ooph for bigger drills. Not good. In this context non-induction usually means inexpensive motor plus inexpensive electronics to meet the price demanded by the marketing guys. Chance of magic smoke escape after a relatively short life is high. Especially as the inherent lower power at lower revs makes it likely that the machine will be overloaded on a regular basis.

DC drives can be very good and very durable. But not at that price.

Clive.

That SIP drill looks to have an induction motor on the back so probably a small three phase unit with inverter control.  Price is just about high enough.  With only a 550 W, 2/3 rds HP, motor will be decidedly wimpy on bigger drills.

 

Edited By Clive Foster on 12/03/2017 17:55:19

[Neil WyattModerator @neilwyatt]

Induction motors have the wired coil in the casing and the coils on the armature are not connected to anything external (they work by induction, like the coils of a transformer, hence the name). No brushes or commutator to wear out means that the service life is generally determined by the bearings and the duty the motor has to perform.

Induction motors require AC drive (just as a transformer won't pass DC) and the frequency of the AC (and number of poles) determine the rotational speed, hence VFDs (variable frequency drives) are used for speed control.

Three phase motors respond better to such speed control because the torque is balanced throughout a rotation, in contrast at low speeds a single phase motor has 'dead spots' where the AC signal crosses zero.

'Universal' motors with field and armature windings will work of AC or DC and can be speed controlled in various ways as they are not synchronous.

Permanant magnet motors are DC only.

Neil

[petro1headParticipant @petro1head]

Cheers guys

That's an interesting comment re the SIP Clive as I was thinking about buying one

So if I wanted to get around changing the belts and have a variable speed like I do with my lathe and mill what would be the most cost effective way of doing it?

(Neil could you change the heading please to something more suitable or should I just start a new thread?)

Edited By petro1head on 12/03/2017 19:22:36

[RobboParticipant @robbo]

I don't know if it is still the same, but Sealey used to sell a variable speed bench drill that worked on the expanding/shrinking pulley system, like some milling machines. Names evade me at the moment, but I will remember them in about ten minutes. This is called "old age cognisance"

So you need to check before you buy. If there is a windy handle sticking out of the headstock that doesn't move the quill, then its probably an expanding pulley system.

Edit.  Chinese motors have been labelled "Induction Motor" for ever.  Nowadays probably left to distinguish them from the more modern electronically controlled motors as fitted to lathes and mills.         European motors for machinery were assumed to be induction motors unless stated otherwise.

Another edit.   just did a search for SIP variable speed drill and was rewarded with the SIP 01533.    This is the one with the expanding pulley.  See the big red knob (oo'er missus) on the left of the headstock. This is the pulley diameter changer I think.      They are remarkably shy about saying how it works, so arousing  "suspicion mode". If it had an inverter controlled induction motor I think they would make a song and dance about it

Edited By Robbo on 12/03/2017 21:10:55

Edited By Robbo on 12/03/2017 21:19:16

[Mike PooleParticipant @mikepoole82104]

I think the term "induction motor" is being used to describe a squirrel cage motor which is a specific type of induction motor. Other types of motor eg slipring are still induction motors but have a wound rotor to allow control of rotor current. An example would be crane motors to allow smooth acceleration by progressive reduction of the external rotor resistance. Just being a bit pedantic as our home workshop equipment is most unlikely to have anything but a squirrel cage motor called an induction motor.

Mike

[Roger Provins 2Participant @rogerprovins2]

The Ryobi 5530L drill press has the expanding pulley system for speed control

Probably the same as the SIP.

Roger

 

 

Edited By Roger Provins 2 on 13/03/2017 00:39:41

[Ian S CParticipant @iansc]

Induction motors can't be too bad. Although the motor was in tip top condition, the blower and moyor of our church organ has been replaced, The motor is a single phase 4 pole 1 hp induction motor with plain bearings, the date on the motor is 1917, so I suppose that after a century it can have a bit of a rest. It is about the size and weight of a modern 5 hp motor, and has a one inch shaft with two bronze bearing bushes at each end with a gap between them for ring oilers, each bush is one inch long, a life like this is probably because of over engineering.

Single phase or three phase, these are the motors for reliable machinery.

Ian S C

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