Will a light dimmer be able to speed control this--

[Mr Sandman]

MMP3 pump on this page. It only uses 90watt of juice.

cheers

Steve

[Tim W]

Mr Sandman wibbled on Monday 07 December 2009 10:01

Don't see why not. My dad used to use a table lamp inline dimmer (BC socket, BC plug and a wide bit with a knob in the middle) to control an electric drill (also had a 13A socket wired to ye olde BC plug, wot earth? *cough*)

The dimmer probably won't mind unless it's very fancy - there may be a bit of electrical noise caused by sending chopped sine waves into a motor.

The pump shouldn't either as long as it's not full of electronics and you don't stall it, whereby it might overheat.

[Peter Parry]

Their data sheet pages appear to be AWOL but it looks to be an induction motor. If so a dimmer will _not_ control the speed which is a function of the number of pole pairs (number of windings in the stator) and the frequency of the supply voltage. You would need an inverter drive to control the speed.

The motors which are easily controlled by dimmers are the "universal" brushed motors used in drills and other hand tools. Noisy, fast and powerful they are not usually found in small pumps.

[John Rumm]

I would have expected a pump like that to use an induction motor. If that were the case then adding a PWM style dimmer may only reduce the torque but leave the speed mostly unchanged.

[Tim W]

John Rumm wibbled on Monday 07 December 2009 10:56

Good point - forgot about induction motors...

[Bob Minchin]

The data sheet says motors are either brushless DC or brushed motors but then does not state which is fitted to the pump you want. It does state 230 AC so possibly is the brushed version in which case it

*may* be happy running on a dimmer. Consult the suppliers.

Bob

[Tim Lamb]

In message , Peter Parry writes

Umm..

You can *speed*control an induction motor driving a fan by reducing the supply voltage. My simple understanding is that the output torque increases more slowly than the square law load imposed by the fan so the motor fan system is stable. There may be other requirements regarding the motor starting arrangement: capacitor start/run perhaps.

I have no idea what sort of load would be imposed by an impeller pumping water.

regards

[John Rumm]

IIUC, most fans use shaded pole induction motors, which are better suited to triac control than more conventional types. Thy have very low starting torques though, which limits their applications to things like fans that are easy to spin up at first.

[Steve Walker]

Just a quick point. When reducing the speed of an induction motor by using an inverter, you also need to de-rate the motor or it may overheat. IIRC due to increased losses in the motor, combined with reduced cooling due to the motor cooling fan generally being driven by the motor shaft and therefore running too slowly.

SteveW

[Bob Minchin]

It also needs to be a 3 phase motor so inverter use is irrelevant to this question.

Bob

Bob

[Steve Walker]

Correct, it must be 3 phase (well you can actually have more than three phases if you really want, but that'd be very non-standard).

SteveW

[Mr Sandman]

Thanks for the discussion chaps, i will find out for sure if it is an induction motor, the one i have is the MMP3 240v single phase model.

Steve

[robgraham]

A late reader of this thread. What about the CH pumps that have several speeds available ? One of the recommendations that appears here fairly regularly for pump-over into the header tank is to reduce the pump speed.

Rob

[Andrew Gabriel]

It's done by reducing the voltage at the same rate you reduce the frequency. This means the torque drops too, but nothing you can do about that. It's OK for things like fans where required torque drops off with reduced speed anyway, but is less suitable for constant torque loads.

Shouldn't get increased losses in the motor if the voltage is being dropped (providing torque doesn't drop too low relative to the load to keep the motor near-synchronous), but loss of integral cooling can be an issue.

[Mr Sandman]

A late reader of this thread. What about the CH pumps that have several speeds available ? One of the recommendations that appears here fairly regularly for pump-over into the header tank is to reduce the pump speed.

Rob

It has to be food grade for home brew, i need to be able to start the pump slowly with all valves fully open to stop them blocking with little bits of grain.

Steve