New blower motor speed control problem

[69800]

My Pacific Energy summit wood stove had a blower motor give up this winter. The fasco motor was a single speed with a factory installed reostat. The new oem replacement motor from Facso is a 3 speed motor. I bought a 3 speed switch at the hardware store and rewired the stove. Now the lowest speed is about the same as the highest speed on the old motor. I would like to slow all the speeds down a little. The motor guys on the net say reducing the voltage to the motor alone is not good for it. They say Typically when you want to regulate the speed of any A/C or D/C motor a variable frequency drive is required. When you lower the voltage you need to lower the frequency also. I can not find an inexpensive controller anywhere. I think my previous two blower motors failed early due to the fact the cheap little reostat supplied by Pacific Energy was just lowering the voltage and it contibuted to the motors early deaths. (about 3 seasons each)

Any one got any ideas?

thank
Mark

B47120 Centrifugal Blower
115 Volts
4 Pole Motor
3 speed
60 frequency
1360/1100/830 RPM @ free air
1.95 amps @ free air

 

[begreen]

Maybe get a speed controller like this: (6A with plate) (broken link removed), (broken link removed) or (3A with plate) (broken link removed), (broken link removed) .

 

[EddyKilowatt]

The "motor guys on the net" are pretty much right... to *properly* change the speed of an induction motor you do need to change the line frequency as well.

Nevertheless there *are* some small fractional-horsepower motors that can achieve variable-speed operation by only changing the line voltage. It is not a super efficient proposition, and the motor will generally warm up and/or hum a bit... but if it was designed with adequate margins to begin with, the warm-up should not greatly reduce life... and at power levels of a few dozen watts, a little lost efficiency won't break the bank or melt the Greenland Ice Cap.

BUT... the big question remains, is the Fasco motor you were sold rated for variable-voltage operation? I can't help there, but I can point you towards this useful page on the Fasco website, where you *might* be able to find your motor's model number (or at least family), and feel a bit more informed about what it can handle.

http://www.fasco.com/fasfacts1.asp

Including this cautionary, though somewhat C.Y.A., advice about speed controls:

http://www.fasco.com/pdf3/page31.pdf

Do you know how your original motor failed... did it overheat, short out, or go open (an electrical problem), or did the bearings dry out and go bad (mechanical problem)?

regards,
Eddy

 

[Bubbavh]

Maybe bypass it and use a router speed control. $14.99 at harbor freight.
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=43060

 

[69800]

Give me the day to check out these links. The old motor feels like the bearing went.

 

[69800]

I think all of the links above are voltage only controllers.. After reading fascos pdf files I think the answer would have been a 6 pole motor which turns lower rpms

mark

 

[begreen]

The Grainger links are for shaded pole motor speed controls. I put the Broan bath fan control on a fasco transflow with a shaded pole motor and it worked great.

 

[raybonz]

Shaded pole motor speed is determined by the frequency and number of poles.. The number of poles is a fixed item so you must control frequency.. Voltage reduction is not the way to go.. I suggest a speed control designed for ceiling fans as they are shaded pole motors however I would advise that you do not run it too slow as this could lead to overheating the motor unless you have the motor externally cooled..

Ray

 

[raybonz]

Maybe bypass it and use a router speed control. $14.99 at harbor freight.
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=43060

These controls are designed for universal motors not shaded pole motors.. Universal motors will run on AC or DC and speed is controlled by varying the voltage to the armature.. Shaded pole motors would not be happy with this speed control...

Ray

 

[EddyKilowatt]

Give me the day to check out these links. The old motor feels like the bearing went.

If the bearings went, then probably the old speed control ("rheostat") isn't what killed it. Unless the hum and vibration is what got 'em, but probably they dried out. Sleeve bearings are only good for a few thousand hours anyway.

If you can't get any specific advice out of Fasco (doesn't look like they're set up to deal with retail customer questions), I think you'd probably be safe to at least try your new motor with the old speed control. Run it for a few minutes, stop and feel the motor and see if its getting hot... run it for several minutes and repeat... then 20 minutes... you get the idea. Give it a sniff, too, for that hot-varnish smell that overheated motors make. (The thing that *might* overheat is actually the rotor, not the stator... so check that if you can.) If you don't detect any major signs of overheating, you're probably good to go.

A drop of light (0-20W) synthetic motor oil on each bearing once per year would probably help them run a little longer... that stuff's good at high temperatures and evaporates more slowly than regular mineral oil.

Eddy

 

[raybonz]

Give me the day to check out these links. The old motor feels like the bearing went.

If the bearings went, then probably the old speed control ("rheostat") isn't what killed it. Unless the hum and vibration is what got 'em, but probably they dried out. Sleeve bearings are only good for a few thousand hours anyway.

If you can't get any specific advice out of Fasco (doesn't look like they're set up to deal with retail customer questions), I think you'd probably be safe to at least try your new motor with the old speed control. Run it for a few minutes, stop and feel the motor and see if its getting hot... run it for several minutes and repeat... then 20 minutes... you get the idea. Give it a sniff, too, for that hot-varnish smell that overheated motors make. (The thing that *might* overheat is actually the rotor, not the stator... so check that if you can.) If you don't detect any major signs of overheating, you're probably good to go.

A drop of light (0-20W) synthetic motor oil on each bearing once per year would probably help them run a little longer... that stuff's good at high temperatures and evaporates more slowly than regular mineral oil.

Eddy

Sleeve bearings will run a very long time if you lubricate them once a year.. My fan is at least 10 yrs. old and still running fine.. If you get the varnish smell then your stator is getting too hot (and probably ruined due to overheating) not your rotor.. Ed I am sure you're knowledgeable however I am a licensed electrician and have worked industrial for over 25 yrs. so I do understand this stuff.. The rotor is simply a large hunk of metal with some fairly good sized copper embedded that rotates due to the voltage induced by the stator which is electrically rotated a bit out of phase causing a rotation effect which makes the rotor go round.. As for lubrication a light straight weight oil such as 10W or perhaps 3in1 is best.. Sleeve bearings are made with sintered bronze which is permeated with oil and will run a long time with low maintenance however a couple drops of straight weight 10W oil once a yr. or so will prolong their demise.. Multigrade oils are not ideal for lubricating bearings ...

Ray

 

[raybonz]

The Grainger links are for shaded pole motor speed controls. I put the Broan bath fan control on a fasco transflow with a shaded pole motor and it worked great.

BeGreen you are right on the money with that recommendation.. Some people although trying to be helpful have given less than ideal advice.. My feeling is that if you are not sure do not give advice and lead people down the wrong road.. Your advice is always well thought out and to the point.. Just my 2 cents..

Ray

 

[69800]

Where this discussion started was the motor guys say its best to use a ****variable frequency drive**** to control speed using frequency rather than voltage.

I really was trying to find one of these units for say under $75 to get max life out of these shaded pole motors.l. With so many around I cant believe no one sells them specifically for this application... You know how many stoves are out there burning up motors due to low volts?.. If I can not find one I am going to find an electronic guy and start producing them. This market has a large hole in it. I am sure fasco would rather not see thier motors last for 15 years but I think they would probably go forever if you kept the bearings lubed.
mark

 

[69800]

Might have found the answer.....

AC Single-Phase variable Speed Drive, 1/8-1.0HP, 110V & 220V: The Optidrive E2 Single Phase is the only available fully digital variable speed drive for controlling low power single phase AC motors. Single Phase-in / Single Phase-out. The E2 is designed to be cost effective and easy to use with compatible single phase motors. The E2 is the most heavily featured yet commercially competitive VFD available in the market. The innovative and compact Optidrive E2 product range combines functionality with robustness, reliability and easy to use programmability.

I and the best part is I can program the fan speed while I on my yacht in the Azores from a sat phone through the gps system in geo sycronys orbit through the internet and reach any rpm + of - .00042 % with guarantied power using an interruptible power supply with a self starting backup generator.

Its only $8300.00 and would probably give the motor a 10 year life span.

I just have not figured out who is going to reload the firebox in the morning....

Oh! Did I just have that dream?

sorry guys

mark

 

[69800]

Just kidding

 

[raybonz]

Just kidding

http://www.electricmotorwarehouse.com/kbwc.htm

(broken link removed)

(broken link removed)

Tons of resources for those who desire speed control on their shaded pole motors.. I prefer the bottom one and use one similar on my bedroom fan, Lutron controls are quieter than many.. Beware some lesser controls can cause a fan to be noisy..

Ray

 

[69800]

Thanks for the info
Mark

 

[EddyKilowatt]

I reckon there's a hole in the single-phase motor speed control market because most small (shaded pole or permanent-split-capacitor) motors can be speed controlled adequately with a simple SCR phase ("lamp dimmer") type control... per Ray's links above. Bigger single-phase motors can't be slowed down much anyway due to their split-phase start winding and switch, thus no market there. Beyond that you get into three-phase motors, either induction or permanent magnet, driven by built-in three-phase inverters (as are beginning to appear in many modern appliances).

Eddy