General Category > General Discussion

Speed regulators

(1/2) > >>

Les Symonds:
What do members think of regulators that can be used with electric motors to regulate their running speed. Is it feasible to buy a regulator and use it to control lathe speed, or is that too simple a solution to the chore of shifting the drive belt frequently? I see regulators on sale on ebay for incredibly cheap prices....seems too good to be true!
Les

john taylor:
Also if you have a run/start capacitor on the motor they wont work.

john

Les Symonds:
Thanks George/John....that casts enough of a shadow for me to think it's not worth it.
Les

Woodcrafts:
Hi Les,
This might be a bit late but if it's of interest, there are two basic forms of speed regulation. The 'cheap' option, in effect pulses the power on and off to the motor, known as Pulse Width Modulation. In effect the motor tries to get to full speed but as the pulse switches off, it then slows down again. However this is happening so fast, the result is the motor appears to be running at a certain speed. The shorter the pulse, the slower the 'speed'. It is the same principal used in filament lamp dimmers. The real downside of this is that you are losing power as well as speed. But these are very cheap controllers.
The other form of speed control uses three phase motors and the controller varies the frequency of the power supply. These motors are quoted to run at a certain speed e.g. 1425 for a four pole motor, but this assumes a 'normal' 50Hz supply. The controller is able to provide the voltage/current at variable frequency, but full voltage/ current, thereby allowing the speed to be changed with minimal loss of power. There are power losses due to other factors but nothing like as bad as 'dimmer' controllers.
Another advantage of frequency controllers is that you can run the motor faster than its nominal speed, as most controllers allow you to set an upper maximum frequency well above 50Hz. Again there are pros and cons of doing that, but it can be very useful by giving you an even wider speed range.
The downside of these is the cost, as you need a more expensive controller and a three phase motor but once you've used a proper variable speed lathe, you won't need much convincing about the benefits.

Les Symonds:
Many thanks, Woodcrafts, that was most informative and not too late by any means. The cheap option (Pulse Width Mod) clearly isn't right for me as my lathe has only a 0.5 hp motor, so I really couldn't afford to loose power at the expense of gaining control over speed. However, the better option of the three-phase motor and controller also poses a problem, in that I don't have a three-phase supply, as my workshop is just a converted garage at my home.
Perhaps I'm stuck with the prospects of shifting drive belts all the time.

Thanks again...Les

Navigation

[0] Message Index

[#] Next page