...are closed loops becoming obsolete?

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you brought up VFD without noting the true application.
 
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IMO, at this point this thread is so far off topic, that it's serving no one...
I enjoyed the debates for the most part but I'm done.
 

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Interesting link provided, but I would take it with a grain of salt. That link came from the manufacture.
Cycle Stop Valves, Inc.



VFD...

http://www.cyclestopvalves.com/vfd-energy_8.html

Most of the articles I have read that claim energy savings when using a VFD control are misleading. If you carefully read these articles you will find that other parameters were changed at the same time as the VFD was installed. Usually the head required was reduced by increasing the pipe size or increasing the NPSHA, the use of a dump valve was discontinued, or a smaller or more efficient pump was installed. Then a VFD is added to the control system and given the full credit for the reduction in energy when it is simply not the case. Other articles have used the Affinity Law to show energy is being saved by the cube of the RPM. However, they neglect to mention that head is lost by the square of the RPM. This limits the minimum RPM possible that will still produce the head required. These articles falsely show incredible reductions in power that go along with reducing the RPM by 50% or more. When in reality the RPM can be reduced by no more than 10% or the head required is no longer attainable. According to the Affinity Law a 10% reduction in RPM produces only a 23% reduction in power consumed, not the 50% or 90% reduction in power that many drive manufacturers would like for you to believe. Only those who lack understanding of how centrifugal pumps really work would claim VFD's save energy.
 

twilliard

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A VFD in today's standards would be not economical in today's aquarium use and the drive itself is only meant to control flow rates through variable frequency. They still generate a ton of heat that is why they are fan cooled, the drive itself.
PWM in a DC circuit creates minimal heat on the control logic and the winding incorporated .
DC in closed loops is gaining grounds but still IMO needs more research to reach the longevity of an ac driven pump.
 

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A VFD in today's standards would be not economical in today's aquarium use and the drive itself is only meant to control flow rates through variable frequency. They still generate a ton of heat that is why they are fan cooled, the drive itself.
PWM in a DC circuit creates minimal heat on the control logic and the winding incorporated .
DC in closed loops is gaining grounds but still IMO needs more research to reach the longevity of an ac driven pump.
I'm curious as to what you think are the best DC pumps in the aquarium market today? You know which ones I am not a fan of.
 

ksed

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Low voltage BLDC pump are definitely more economical than VFD, but we are discussing which are more energy efficient. I can tell you that Royal Exclusiv and Abyzz don't use PWM. Also not all VFD need a fan. Take a look at controllers used buy the manufactures listed above.


A VFD in today's standards would be not economical in today's aquarium use and the drive itself is only meant to control flow rates through variable frequency. They still generate a ton of heat that is why they are fan cooled, the drive itself.
PWM in a DC circuit creates minimal heat on the control logic and the winding incorporated .
DC in closed loops is gaining grounds but still IMO needs more research to reach the longevity of an ac driven pump.
 

twilliard

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I'm curious as to what you think are the best DC pumps in the aquarium market today? You know which ones I am not a fan of.
Any that are PWM controlled
Hands down the best in energy consumption savings.

Its not who is about the best, its who employs today's technology
 

twilliard

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Low voltage BLDC pump are definitely more economical than VFD, but we are discussing which are more energy efficient. I can tell you that Royal Exclusiv and Abyzz don't use PWM. Also not all VFD need a fan. Take a look at controllers used buy the manufactures listed above.
Now are you talking aquarium use or industrial use?
I can go on all day about industrial use :) been doing it for 20 years
 

ksed

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Again you are misinforming the public. You clearly don't know how to refrain from posting info that caters to your best interest. So when you are saying that a DC motor only uses PWM, that is incorrect. What about trapazoidal, sinusoidal, and FOC. BTW FOC is the best:p

If you can control a DC motor it is using PWM :)
 

twilliard

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Again you are misinforming the public. You clearly don't know how to refrain from posting info that caters to your best interest. So when you are saying that a DC motor only uses PWM, that is incorrect. What about trapazoidal, sinusoidal, and FOC. BTW FOC is the best:p
I am talking about today's aquaria use :) its all PWM :)
 

twilliard

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Again you are misinforming the public. You clearly don't know how to refrain from posting info that caters to your best interest. So when you are saying that a DC motor only uses PWM, that is incorrect. What about trapazoidal, sinusoidal, and FOC. BTW FOC is the best:p
Lol why in the world would I misinform the community that I am devoted to?
PWM is the key :)
 

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