Variable Speed Controller for Single Phase Motor

[Mkraft]

Looking for opinions here. I have an application where I need to vary the speed of a single phase motor. In my research I have found that this is possible using a variable voltage source (like a cieling fan controller) or a controller that varies the frequency and voltage using pulse width modulation. Obviously a traditional capacitor start motor with a centrifical switch wouldn't work with variable voltage, so a Permanant Split Capacitor motor, a Shaded Pole motor, or a Univeral motor have been suggested by various controller manufacturers. I'll be controlling the speed via a 4-20 mA signal from PLC, so a cheap fan controller won't work, but some of the dedicated controllers are too expensive for this job. Accuracy of speed control isn't much of a factor because it's on a ventilation fan. Any ideas of what to use? Brands? Concerns with the application? Thanks, Mark

 

[electricuwe]

To my mind you should remove the following approaches from your list:

Shaded pole motor (efficiency very low)
Universal motor (maintanance of brushes, this type of motor is usually used for variable speed drives where the number of operating hours is quite low e.g hand-held drills)

The permantent split capacitor motor can't be used with variable frequency control but may be used with variable volatge control, but I haven't seen a dvice intend for that purpose.

So from the options given ther isn't much left. Depending on th power ratin I would suggest the following approch:

I do not understand for what reason you are limited to a single phase motor. If the supply is the only limit there are following options:

Low power (may be up to 200 W)
Use a DC or brushless DC motor together with a suitable power supply

higher power
Use a small inverter (variable frequency VSD) with single phase input and three phase output together with a three phase induction motor

 

[jbartos]

Suggestion: A permanent magnet synchronous motor with a variable frequency drive could be considered.

 

[hentied]

Question: Wouldn't it be possible to make use of a single phase in / three phase out inverter and then connecting the single phase motor to the inverter in such a way to vary the speed. Only connect to one / two? of the three inverter output phases.

I have heard that it is possible with some of the new manufacturers vfd's and am now trying to find out how one should go about connecting this system.

I have a single phase motor pump and a single phase supply / three phase out inverter that i would like to control in a similar fashion.

Any ideas?

 

[Lewish]

I wouldn't recommend putting a single phase motor on a 3 phase VFD. The VFD is designed around the parameters of a 3 phase motor and depends on all those parameters being present for proper operation.

 

[SteveKW]

Hentied
Your idea would work, just use a three phase motor.

 

[jbartos]

Suggestion: Visit

http://www.infomicom.mesc.co.jp/M16C/efaq/e3phase.htm#3phase2

which deals with the single phase motor control over 3-phase motor control.

 

[GSI1]

First using a single phase motor on a variable freq drive will not work. If the motor is run at a speed slower then the rated speed the start switch could pull in and the motor would run in start mode all the time. This would burn up the motor in a short time.
Why not just use a. Inverter with a 3Ph motor. you can get Inverters that are raited 120 VAC 1Ph in and 230 VAC 3 Ph out. most new stile inverters will work on single phase input ( Just reduce the output current by 30% )

 

[jOmega]

1st, you cannot run a single phase motor on a 3-phase VFD. While you may get the motor to rotate, you might want to standby with a fire bottle to cool it down when it burns up.
(Don't you just love the smell of overheated linseed oil !)

2nd PSC motors can and do indeed lend themeselves to variable speed operation with variable voltage/variable frequency control. Fan drives are an excellent application.

Anacon Systems is a company providing variable speed control
solutions for variable speed control of AC motors. They provide variable frequency drives for both single-phase and three-phase AC induction motors. They have been providing the single phase solution for many years, and have recently added three-phase drives to their product line.

Their single-phase solution with PSC type motor is proper for a variable torque (cengrifugal type load ... fan, pump)... and typically works well down to about 40% speed. Below that it gets a bit iffy. However, their latest product offering may allow you to operate down to 20-25% speed....

http://www.anaconsystems.com

 

[jbartos]

Suggestion: Visit

http://www.franklin-electric.com/sub_cat/pdf/M1302.pdf

http://www.franklin-electric.com/sub_cat/pdf/M1301.pdf

http://www.reliance.com/prodserv/motgen/acmothome.htm

http://www.saftronics.com/pages/literature2.htm

etc. for potential motor and drive manufacturers opinion.

 

[GSI1]

jOmega
I checked you link go back and check again you will notice they are using
PSC (Permanent-Split-Capacitor)or Shaded-Pole Single-Phase induction motors only.
Both of those can be controlled with almost any household dimmer switch.

Not very practical in the real world. But yes if you want to limit the usage to a fan in you house go for it. Most single phase motors have a centrifugal switch, this switch is used to disengage the start winding after the motor is up to speed id the motor speed falls down to the point where the switch closes again the start winding will again draw current over heat. It’s just not worth it. Small 3 ph motors are easy to get and are cheap. Their are Inverters out there that have a built in voltage doublers that will work well with 120 vac in and provide 0 to 240 vac at 0 to 400 HZ output.

 

[jOmega]

GSI1,

Here are the spec on one model of the Anacon offering...

EagleDriveTM 1

An industry-first, designed for use with Single-Phase AC Induction motors and is available in 115V or 230V at power levels up to 1.5 HP.


--------------------------------------------------------------------------------
Key Features:
Single-phase input/single-phase output
Push-button keypad as standard
Variable Torque or Constant Torque
Drive efficiency typically 95%
Optional Filters to meet EMC standards
Meets UL, CSA (UL508c), CE (EN60204-1, EN50081)
Speed range of 0-100 Hz
Ten (10) selectable V/f curves available
EagleEyeTM - remote control, hand-held programmer (option)
EagleVisionTM - WindowsTM based application program to store parameters and data (option)
-------------------------------------------------------------------------

Which light dimmer would you recommend to provide the same performance as listed in the above key features .... particularly the 0-100 Hz speed range and the Ten (10) selectable V/f curves...? ;-)