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09-12-2007, 09:51 PM #1
Variable speed drives for single phase motors
Gentlemen
Here is another one which i have been wondering about for quite sometime. I have to upgrade a wing of an office building and install variable air volume diffusers to achieve my goal. This dictates that i should vary the air volume from the air handing unit as well. My problem is i should use the existing AHU and it has 3 single phase supply air fans. I have never seen a single phase inveter. Can someone tell me a brillliant idea to use.
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09-12-2007, 11:49 PM #2
Re: Variable speed drives for single phase motors
Do you have a three phase supply available in the building that you could use ?
Brian - Newton Abbot, Devon, UK
Retired March 2015
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10-12-2007, 12:06 AM #3
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Re: Variable speed drives for single phase motors
You could connect these three fans in star as one three phase fan motor and regulate speed with one three phase inverter.
Last edited by nike123; 10-12-2007 at 07:26 PM. Reason: wrong statement
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10-12-2007, 05:54 AM #4
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10-12-2007, 06:06 AM #5
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10-12-2007, 06:11 AM #6
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10-12-2007, 08:39 AM #7
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Re: Variable speed drives for single phase motors
I didn't done that before but I don't see to many reasons why this should not be working satisfactory in practice if you carefully set min. and max. sped. It is similar to conventional PWM by thyristor or triac in conventional fan speed regulators
This could be of some value to you:
http://tinyurl.com/3yb7sr
http://tinyurl.com/yswttm
http://tinyurl.com/387tge
http://tinyurl.com/2lybnj
Last edited by nike123; 10-12-2007 at 10:23 AM. Reason: adding links
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10-12-2007, 10:17 AM #8
Re: Variable speed drives for single phase motors
alternatively you could use a motorised damper in conjunction with a static pressure sensor to meter the air. Although this would involve some clever control.
You could also use a single phase stepped speed control (transformer type) or a three phase version but you would have to introduce protection on the transformer output side on each.
Phase chopper speed controllers are available for single phase applications but they are generaly only suitable for low load/ torque.
all that aside I would rip out the three fans and put a 3 phase fan in
good luck
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10-12-2007, 10:23 AM #9
Re: Variable speed drives for single phase motors
Nikes idea will work but....
an invertor will probabley pickle itself as you have a greater scope for phase balance faults as the 3 fans will inevitabley load up differently (especially when speed changes occur). My advice is dont do it unless you have time and money to spare
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10-12-2007, 12:22 PM #10
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Re: Variable speed drives for single phase motors
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10-12-2007, 07:23 PM #11
Re: Variable speed drives for single phase motors
Thank you guys for all the insights that you are giving me. This forum is such a good idea.
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