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Thread: Variable Speed for 1/3HP Motor
02-15-2012, 03:00 PM #1
Variable Speed for 1/3HP Motor
We have several fans for our livestock. They are
220V 1PH either 1/4HP or 1/3HP. We want to vary
the speed of them to control temperature better.
We look and find controls that cost $213.00
@ 7amps max.
Surely there is something out there that
can do this cheaper. There is no precision
here just 25% to 100%.
Thanks for any help!!
olf20 / Bob
02-15-2012, 04:10 PM #2
Cheapest solution is to change the motors for 3 phase and buy NOS vfds for them. An ordinary single phase induction motor cannot be run as variable speed, the controls you mention must be specially matched to some particular motor(possibly 3 phase or multi speed) You can also use a control to spoil the input or output of the fan so it moves less air at full speed.
02-15-2012, 05:07 PM #3
These motors are just off the shelf Grainger motors.
We have replaced several of them. The control that
cost $213 is not for any specific motor. Just 220V.
They are wired with one leg direct to the motor
and the other leg is wired thru the control.
Here is the document for the controller.
Thanks for your reply.
olf20 / Bob
02-15-2012, 05:33 PM #4
Sorry, I was thinking of exhaust fans that use ordinary induction motors, not ''fan'' motors. I think that control is probably a glorified light dimmer, but i will wait for somebody qualified to answer.
02-15-2012, 08:08 PM #5
Tell me, Bob...
In looking at that controller, and re-re-reading your question....
Does that controller simply turn the fan array on and off based on temperature setting? Zooming in close to the controller board doesn't reveal any hints of substantial componentry.
With the stirring-fan motors I've seen, they're an arrangement that will SOMETIMES respond okay to a thyristor-chopper type control, like the 'dimmer' type that Rob mentions, but if you're running an array of stirrers in your pen, and they're on 240v line, you can't just use a 120v dimmer.
One COULD, however, employ a gadget that uses a solid-state relay and switches power on and off... a few cycles on, and then a few off... so that the motors are never really running 'at speed'... the downside is that some motors will get really hot under those circumstances.
If I were faced with this situation, I'd probably consider something half-luddite... take the motor out, and install a shaft on each frame so the fan blades could be belt-driven from a lineshaft, and then put a 1hp 3-phase motor at some convenient location, and VFD that bugger, and wire the VFD to a thermistor sensor, so that fan speed increases with ambient temperature, and put the thermistor in such a location that airflow provides direct feedback to the thermistor's sense location, which means the temperature will attempt to be made self-regulating and constant based on your setpoint.
02-16-2012, 04:42 AM #6
Their diagram just show one application. Our is different, one fan on each
side of the building. I talked to the tech on this control and he said it did
not matter how many motors were hooked up as long as the total current
did not exceed the max for the controller.
Thanks for you responses!
olf20 / Bob
02-16-2012, 06:42 AM #7
That controller is reducing voltage. That would be ok on a hand drill or something like that, but a plain motor will try to run at full speed and starve for voltage if the hertz are still 60.
I would point you toward a VFD and 3 phase motor.
1/2HP, TB Woods, Model SE1C2S005H01, 230 Volt 1 Phase Input, variable frequency drive, variable frequency drives, ac drive, vfd, afd, frequency drive, drive, inverter, adjustable speed drive - Dealers Industrial Equipment, LLC
GE 1 1/2 hp 5K182AL313B Motor (MOT2103) | eBay
RELIANCE AC MOTOR P56H0302N-PT 1/2HP 230/460VOLTS ***NNB*** | eBay
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Shop carefully, there is a lot of stuff around.
02-16-2012, 12:01 PM #8
These are used in a lot of farm applications. We have had other
controllers that vary the speed of the fans as well as control
The three phase option is a little more difficult because of wiring
and getting motors to fit inside our fan enclosures. Many of the
farm fans have a complete fiber glass or stainless steel housing
and the motor and fan fit inside.
Thanks again for all input.
olf20 / Bob
02-16-2012, 12:46 PM #9
This will work for Shaded Pole motors, which is what those Stir fans are, just like your paddle ceiling fans. From the little bit of info they provide on that controller, I'd guess that this is nothing more than a simple triac controller with a bypass switch, basically a 12A dimmer and a parallel switch rated for 12A. You could make the same thing out of off-the-shelf parts if you were so incliuned. 12A at 230V is roughly 2000W worth of motor load, so that thing would be overkill for one single motor of 1/3HP. An off-the-shelf fan speed control would be a lot less expensive. But you will need to pay attention to how you house it, the points they make in their data sheet about ambient conditions are valid.
Don't use just any lighting dimmer, some of them are not suitable for motor loads.
Fan Speed Control, 3 A - Fan Speed Control - HVACR and Appliance Controls - 1DGV1 : Grainger Industrial Supply
02-16-2012, 04:06 PM #10
Thanks for your reply Jraef. So I would just wire it as
per the diagram in the PDF file, on one leg of the
220? L1 ----- O ------XXXX------- L2
---------- Motor -- Controller
Also thanks for the link.
Would one of the other speed controllers that have
a higher current / watt rating give us a little over kill
to help in the heat of the summer?
Thanks olf20 / Bob
02-16-2012, 05:56 PM #11
02-17-2012, 05:18 AM #12
So it does not matter the controller is 110V and our
motors are 220V?
olf20 / Bob
02-17-2012, 07:57 PM #13
Just trying to get the voltage clarified.
Thanks olf20 / Bob
02-17-2012, 09:35 PM #14
Den, the reason why Bob won't be changing the motors in the fans, is because the fan motor is specific to the fan... built into the framework, not at typical multipurpose motor.
02-17-2012, 11:00 PM #15
For that matter, the maker of the TB woods units also makes single phase VFDs which will work on any motor that the controller shown would.
The dimmer types all ONLY work on a fan type load..... they relay on teh fact that the shaded pole and PSC motors can tolerate lots of slip, and that the fan load varies with speed..... If there were a constant load, or no load, the motor would either not run, or it would go at nearly full speed.
With a single phase VFD, it can be made to go at most any speed more or less regardless of load.
here is the manufacturer in question with single phase VFDs:
Invertek Drives AC Drives, Drives, Inverters, and Control Systems
Last edited by JST; 02-18-2012 at 02:36 PM.