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Can anyone tell me the difference between an induction motor and a brush type motor.
Carba-tec and Timbercon both have a 1HP portable dust extractor - capacity of 600cfm and weight of 22kg.
Timbercon also have a 1HP portable dust extractor - brush type - with a capicity of 914cfm and weighing 9kg.
The brush type has greater capacity and is much smaller - so what is the catch???
Thanks
Don
Hello Don,
Without digging out a book, I've been given to understand that induction motors use less electricity but require a bit more on startup. My thicknesser, bench planer and dust extractor all have induction motors but they nearly spin the electricity meter off its axis in the inital startup. I've had them for 10 years now and haven't had any problems.
Induction are more robust usually fully sealed the best being squirrel cage wave wound totaly enclosed fan cooledQuote:
Originally Posted by Don Nethercott
if fully sealed no dust
& even more important no brushes to wear out and have to be replaced
especialy as you will proberly be running extractor for long periods
The trouble with life is there's no background music.
don't forget that induction moters are quieter as well
Hi Don, I'll try to restore my own scholastic knowledge about electrical engineering: if I don't remember wrong, brush motors are motors which have two small pieces of grafite which conduce current to the rotor.The other doesn't have the two pieces af grafite and works on the principle of a rotating magnetic field.Quote:
Originally Posted by Don Nethercott
The first has the disadvantage that with use the brushes wear and they must be replaced.
On the other hand these motors have (with same size) more HP power.
What type depends what one wants.
It is true that the type without brushes is more sturdy (very much).
Only for your knowledge, the motor of our the electric drill is the brushes type while the motor which is in all industrial machines is the type with rotating magnetic field.
I hope to be been clear..and not have created confusion..
I'm with Noodle Boy, the induction motors are much quieter. Compare the triton to the TSC10HB. :D
This has been thoroughly covered by the rest of the folks, but I still gotta add in a bit. ;)
A brushed motor, aka: universal motor, does have brushes that send power to the rotating part. That spinning part has many segments, which, when the motor is running behave kinda like switches turning some of the rotor (spinning bit) on while turning other parts off. While that's happening, the outside of the motor also has power run through it to make a stronger (than fixed, non-electric) magnetic field. As the rotor's parts are turned on and off, they are trying to catch-up to and push away from the magnetic field created on the outside of the rotor. That's about it really. Bad points are that brushes and the copper coloured part (commutator) wear over time, plus the fact they need to have air moving through them to keep them cool. Both to let brush dust out and cooling air in. Good points are big power from a small package, but you have to stuff in more power to get it. They will also run on virtually any electrical current you can feed them. Which is why many PC routers say they can run on xyz volts, AC or DC.
The induction motor works differently. It only has the outside part of the brushed motor with power running through it. The rotor has no power applied to it through brushes. So that big magnetic field is running around the outside, changing direction 50 times a second. If done correctly, you can have a magnetic field that is constantly running around the outside of the casing, which is exactly what they do. While that field is growing and shrinking, it induces current in the rotor, so it too has an electromagnetic field running through it. Difference is that it's being created as a by-product of the outer field growing and shrinking. Throw in a start winding that is just a little ahead or behind the main wiring and tell the rotor which way to go when starting and you got your induction motor. What kinda happens is the field runs around the outside, it makes a magnetic field occur in the rotor that kinda chases the field magnety thingy around, while also surfing the same field. Dog chasing it's tail or something like that. Good points are to get the same power as a brushed motor, you don't need so much current, so they are cheaper to run. They also have 1 moving part that is usually running on ball bearings. As long as you don't overload it, they will pretty much run forever with the occasional bearing change. Also quiet and can be sealed from dust and such. Bad points are they are usually big and heavy, and more expensive to buy from the start. They also don't like to be started and stopped unless designed for it, which costs more money again.
For your dust collector there, if it needs to be portable and only needed occasionally, go for the brush motor version. If you want the thing to last for a while and will be used often (but left running, not stopped and started) go with the induction motor.
Brushed motors lend themselves well to some things, induction motors are better for other things. In this case, I'd always prefer an induction motor, but occasionally brushes are just the ticket.
If that helps, great. If not, explain what it all means to me because I don't really know what I bashed in there anymore. ;)
Great summary Schtoo,
my 2 bob is that from a user perspective the difference is
a) size for power -> Induction motor is bigger and heavier
b) torque characteristic (turning power) -> Induction motor has little torque at startup. When running if they are overloaded, they stall suddenly. Universal motor (brush motor) has heaps of starting torque. Load up a brush motor and they will fight all the way to stall .. when much smoke emits :eek:.
c) Single phase induction motors need special techniques to get them going (starter windings) ... slow them down too much and the starter kicks in ... it is only rated for intermittent use -> death of starter!
d) Speed -> induction motor just less than 3000 rpm max for a single pole machine on 50Hz AC, Universal motor speed is limited by friction (routers, angle grinders are Universal motors) and they go fast!
e) noise .. as said, the banshee of a universal motor has lead to curfews on their use in residential areas.
As a load a fan/blower is ideally suited to an induction motor. There is no starting torque to overcome, speed match is about right and if fan chosen correctly for the motor, then no risk of overload as the fan has a nice load torque curve etc etc. I'd tend to consider the induction motor more favourably unless portability was really a big issue.
As previously stated an induction motor is quieter.
Also they last longer than a brush motor as they have less moving parts.
The brush motor dusty seems to have a performance edge on the older induction model
BUT
most brush motors won't stand up well to non stop use for days at a time, and
the noise factor of higher rpm and small impeller may limit its versatility because of the effect of noise on neighbors, if not in the workshop.
As a comparison, my blower\vac has lots more suction and volume than my 1hp dusty but I wouldn't like to have listen to its noise for hours on end.
I for one would love to see Dean do a review of the brush dusty.