speed control of AC motors - Electronic Circuits Projects Diagrams Free

hamid · 25th August 2004, 12:05 PM

dir sirs,
with the best regards,
I would be grateful if you give me full information about

electrical speed control of AC motors (one phase) and

give me design(s) and electerical circuites plans if it's

possible.
AC motors that i want to control their speed have

following specifications:
1) 220-230 Volt (one phase)
2) 10 to 25Amper(variable for different kinds of motors)
3) 1 to 5 HP (variable for different kinds of motors)
4) about 1440 rpm
i would be glad if you answer the following questions

too:
1-is there any damages to AC motors if speed of them

controled electrically,and which effects has this

control on their efficiency and lifetime?
2-is this possible that i use both together a nonvariable

gearbox to have higher power and electrical speed control

,and which effects has this way on motors efficiency and

lifetime?
thank you,
yours sincerely,
H.Khoshniat

hotwaterwizard · 26th August 2004, 03:51 AM

Here is the best I could do for now.

http://www.southgatearc.org/techtips/drillspeed.htm

http://mmd.foxtail.com/Tech/PPCo1.html

http://members.shaw.ca/novotill/CeilingFanSpeedControl

yousafsalim · 12th June 2007, 02:13 PM

Hi there, I need someone's HELP related to AC n DC Motors that their CONSTRUCTION, why we USE them, their APPLICATIONS.................and all related to this TOPIC. I got EXAM next week so it should be appreciated, I definitely need someone's HELP. Please HELP me out.

Thanks

picbits · 12th June 2007, 03:01 PM

Another newbie bumping up a post that is almost 3 years old asking for help for their exam ..........

mneary · 15th June 2007, 02:56 AM

@yousafsalim, everything you need to know is already posted here.

Please be specific in your request, but do not include actual exam questions.

Hero999 · 17th June 2007, 03:07 PM

Are these AC motors with carbon brushes, i.e. universal motors rather than true AC motors?

The circuits that hotwaterwizard posted will work with universal motors but not with real AC motors, induction motors.

It isn't easy to speed control AC motors, especially single phase AC motors, in fact it's nearly impossible in most cases, unless it's an especially designed motor.

This site gives a good explanation:
http://www.epanorama.net/links/motorcontrol.html#ac

Quote:

Induction motors are practically fixed speed devices. The there is practically only two methods to change the rotation sped of AC induction motor: use frequency converter or use motor with sperate winding for different speeds. In some applciations motors with dual speed winging are used. The applications where accurate speed control is needed, you need s frequency converter. A frequency converter can run a three phase AC motor at very wide speed range quite well (the performance of motor is usually reduced outside it's optimal operation speed).

There are variable frequency drives that allow induction motors to run on different speeds. But on those applications mechanical load and the speed range must be considered, because on those applications motors can get very hot very fast. The problem is that a 60 Hz (or 50 Hz) motor does not have enough iron in it to allow efficient 25 Hz operation. The motor will run hot due to not having enough inductive reactance at the reduced frequency. Dropping down to 10 Hz would make it even worse. A motor designed for variable frequency drive has more iron. Also, it might use a different iron/steel alloy to allow efficient operation at higher frequencies (say 400 Hz). With a light mechanical load and a good motor combined with a good vraible frequency drive controller, it's sometimes possible to get a reasonable speed range using a variable frequency inverter. A good vriable frequency drive device controls both frequency and voltage. The better ones even take into account that at very low speeds the resistance of the coils cannot be negelected. In VFD (variable frequency drive) system the incoming single phase power is rectified and filtered, and three-phase power is generated from the DC rail using three half-bridges. You get to set the frequency over a range so you can vary the speed of your motor, plus a nice digital display etc. It's a bit harder on the motor insulation than just running it from the line, but well-designed motors should be okay. The reason why VFD is hader for motor insulation is that the unductance in the wiring to the motor allows spikes and ringing at the motor itself. The waveforms that go from VFD to motor are typically quite far from ideal sinewave.

Frequency converter does not work with AC induction motors that are run from single phase power source, because the operation of the needed motor phase conversion capacitor is very frequency sensitive (works as expeted only at normal mains frequency).

25th August 2004, 12:05 PM	(permalink)
hamid New Member	speed control of AC motors dir sirs, with the best regards, I would be grateful if you give me full information about electrical speed control of AC motors (one phase) and give me design(s) and electerical circuites plans if it's possible. AC motors that i want to control their speed have following specifications: 1) 220-230 Volt (one phase) 2) 10 to 25Amper(variable for different kinds of motors) 3) 1 to 5 HP (variable for different kinds of motors) 4) about 1440 rpm i would be glad if you answer the following questions too: 1-is there any damages to AC motors if speed of them controled electrically,and which effects has this control on their efficiency and lifetime? 2-is this possible that i use both together a nonvariable gearbox to have higher power and electrical speed control ,and which effects has this way on motors efficiency and lifetime? thank you, yours sincerely, H.Khoshniat

26th August 2004, 03:51 AM	(permalink)
hotwaterwizard Experienced Member	Here is the best I could do for now. http://www.southgatearc.org/techtips/drillspeed.htm http://mmd.foxtail.com/Tech/PPCo1.html http://members.shaw.ca/novotill/CeilingFanSpeedControl __________________ John DeRosa (Hotwaterwizard) hotwaterwizard@aol.com

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12th June 2007, 02:13 PM	(permalink)
yousafsalim New Member	Hi there, I need someone's HELP related to AC n DC Motors that their CONSTRUCTION, why we USE them, their APPLICATIONS.................and all related to this TOPIC. I got EXAM next week so it should be appreciated, I definitely need someone's HELP. Please HELP me out. Thanks

12th June 2007, 03:01 PM	(permalink)
picbits Experienced Member	Another newbie bumping up a post that is almost 3 years old asking for help for their exam ..........

15th June 2007, 02:56 AM	(permalink)
mneary Experienced Member	@yousafsalim, everything you need to know is already posted here. Please be specific in your request, but do not include actual exam questions.