shaded pole motor control
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From: ontherails on 29 Jun 2010 18:00 > >Does anyone have experience with speed control of a small shaded pole >motor about 25W, with a ghastly PF of about 0.36 ?. > > This drives the water circulation pump in an experimental setup much too >hard, and the churning >measurably heats the water. > >I thought a variable frequency inverter might be nice, but wondered how >sinusoidal it would need to be. I doubt that a simple phase shift let-it- >slip-more controller, would be good enough. Works for fans up to a point. > >Rather than suck it and see, I thought I'd politely probe the brains of >the experts first. > >All the best >Ian Macmillan > > > > Use my variable inductance controller. Carry out this simple experiment to see how it works. Get a 100VA transformer, something like 240V to 40V. Put the 240V windings in series with the motor and connect to the mains - nothing happens. Short the 40V windings - motor runs at nearly full speed but you are still working with AC. Put a bridge rectifier on the 40V windings and short the DC output. Motor runs at nearly the full speed it did before but now you are working with DC. Put a transistor (I normally use a darlington - TIP121 for a 40V secondary and add simple control electronics. You can normally get up to about 90% full speed. Approximately 10% losses occur in the transformer, bridge rectifier and darlington. This could be reduced by using a higher voltage secondary and a MOSFET when the losses could be 5% or lower. The control electronics side is isolated by the transformer so you are working with low voltage DC. Have fun experimenting but beware of the 240V on the transformer. Peter --------------------------------------- Posted through http://www.Electronics-Related.com
From: Martin Riddle on 29 Jun 2010 18:08 "ontherails" <peter.elbro(a)n_o_s_p_a_m.btinternet.com> wrote in message news:HuOdneLxDs1-8bfRRVn_vwA(a)giganews.com... >> >>Does anyone have experience with speed control of a small shaded pole >>motor about 25W, with a ghastly PF of about 0.36 ?. >> >> This drives the water circulation pump in an experimental setup much >> too >>hard, and the churning >>measurably heats the water. >> >>I thought a variable frequency inverter might be nice, but wondered >>how >>sinusoidal it would need to be. I doubt that a simple phase shift >>let-it- >>slip-more controller, would be good enough. Works for fans up to a >>point. >> >>Rather than suck it and see, I thought I'd politely probe the brains >>of >>the experts first. >> >>All the best >>Ian Macmillan >> >> >> >> > Use my variable inductance controller. Carry out this simple > experiment to > see how it works. Get a 100VA transformer, something like 240V to 40V. > Put > the 240V windings in series with the motor and connect to the mains - > nothing happens. Short the 40V windings - motor runs at nearly full > speed > but you are still working with AC. > > Put a bridge rectifier on the 40V windings and short the DC output. > Motor > runs at nearly the full speed it did before but now you are working > with > DC. Put a transistor (I normally use a darlington - TIP121 for a 40V > secondary and add simple control electronics. You can normally get up > to > about 90% full speed. > > Approximately 10% losses occur in the transformer, bridge rectifier > and > darlington. This could be reduced by using a higher voltage secondary > and a > MOSFET when the losses could be 5% or lower. The control electronics > side > is isolated by the transformer so you are working with low voltage DC. > > Have fun experimenting but beware of the 240V on the transformer. > Peter > Shaded pole motors need variable voltage to control their speed, Buck the voltage as described above. Cheers
From: Artemus on 29 Jun 2010 18:24 > >Does anyone have experience with speed control of a small shaded pole >motor about 25W, with a ghastly PF of about 0.36 ?. > > This drives the water circulation pump in an experimental setup much too >hard, and the churning >measurably heats the water. > >I thought a variable frequency inverter might be nice, but wondered how >sinusoidal it would need to be. I doubt that a simple phase shift let-it- >slip-more controller, would be good enough. Works for fans up to a point. > >Rather than suck it and see, I thought I'd politely probe the brains of >the experts first. > >All the best >Ian Macmillan > If you don't care about efficiency and don't need variable speed a power resistor in series with the motor is the simplest solution. Experiment with a variac to see what voltage you need on the motor and determine the ohms needed. Or just leave the variac in place. Art
From: Jim Thompson on 30 Jun 2010 18:34 On Tue, 29 Jun 2010 17:00:03 -0500, "ontherails" <peter.elbro(a)n_o_s_p_a_m.btinternet.com> wrote: >> >>Does anyone have experience with speed control of a small shaded pole >>motor about 25W, with a ghastly PF of about 0.36 ?. >> >> This drives the water circulation pump in an experimental setup much too >>hard, and the churning >>measurably heats the water. >> >>I thought a variable frequency inverter might be nice, but wondered how >>sinusoidal it would need to be. I doubt that a simple phase shift let-it- >>slip-more controller, would be good enough. Works for fans up to a point. >> >>Rather than suck it and see, I thought I'd politely probe the brains of >>the experts first. >> >>All the best >>Ian Macmillan >> >> >> >> >Use my variable inductance controller. Carry out this simple experiment to >see how it works. Get a 100VA transformer, something like 240V to 40V. Put >the 240V windings in series with the motor and connect to the mains - >nothing happens. Short the 40V windings - motor runs at nearly full speed >but you are still working with AC. > >Put a bridge rectifier on the 40V windings and short the DC output. Motor >runs at nearly the full speed it did before but now you are working with >DC. Put a transistor (I normally use a darlington - TIP121 for a 40V >secondary and add simple control electronics. You can normally get up to >about 90% full speed. > >Approximately 10% losses occur in the transformer, bridge rectifier and >darlington. This could be reduced by using a higher voltage secondary and a >MOSFET when the losses could be 5% or lower. The control electronics side >is isolated by the transformer so you are working with low voltage DC. > >Have fun experimenting but beware of the 240V on the transformer. >Peter > > > > >--------------------------------------- >Posted through http://www.Electronics-Related.com Interesting! What kind of (stable) speed range can you get? ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Obama: A reincarnation of Nixon, narcissistically posing in politically-correct black-face, but with fewer scruples.
From: JosephKK on 1 Jul 2010 07:06
On Tue, 29 Jun 2010 17:00:03 -0500, "ontherails" <peter.elbro(a)n_o_s_p_a_m.btinternet.com> wrote: >> >>Does anyone have experience with speed control of a small shaded pole >>motor about 25W, with a ghastly PF of about 0.36 ?. >> >> This drives the water circulation pump in an experimental setup much too >>hard, and the churning >>measurably heats the water. >> >>I thought a variable frequency inverter might be nice, but wondered how >>sinusoidal it would need to be. I doubt that a simple phase shift let-it- >>slip-more controller, would be good enough. Works for fans up to a point. >> >>Rather than suck it and see, I thought I'd politely probe the brains of >>the experts first. >> >>All the best >>Ian Macmillan >> >> >> >> >Use my variable inductance controller. Carry out this simple experiment to >see how it works. Get a 100VA transformer, something like 240V to 40V. Put >the 240V windings in series with the motor and connect to the mains - >nothing happens. Short the 40V windings - motor runs at nearly full speed >but you are still working with AC. > >Put a bridge rectifier on the 40V windings and short the DC output. Motor >runs at nearly the full speed it did before but now you are working with >DC. Put a transistor (I normally use a darlington - TIP121 for a 40V >secondary and add simple control electronics. You can normally get up to >about 90% full speed. > >Approximately 10% losses occur in the transformer, bridge rectifier and >darlington. This could be reduced by using a higher voltage secondary and a >MOSFET when the losses could be 5% or lower. The control electronics side >is isolated by the transformer so you are working with low voltage DC. > >Have fun experimenting but beware of the 240V on the transformer. >Peter > > Gosh that is only about 40 years old. Over 75 if you count tubes. |