VFD Efficiency Loss?
VFD Efficiency Loss?
(OP)
Does anybody have any ideas on the losses through VFD's? I'm guessing they vary among manufacturers, but is there a rule of thumb, a max that could be expected, etc?
I'm doing an evaluation on blowers for a wastewater treatment plant, which are major power users. The PD type blowers are less expensive, not quite as efficient, and require VFD's to throttle flow. The turbo compressors are significantly more expensive, more efficient, and will utilize soft starts.
I'm trying to do a fair 20-year cost analysis and a loss through a drive should be accounted for.
Any help would be appreciated.
Thanks,
Mike
I'm doing an evaluation on blowers for a wastewater treatment plant, which are major power users. The PD type blowers are less expensive, not quite as efficient, and require VFD's to throttle flow. The turbo compressors are significantly more expensive, more efficient, and will utilize soft starts.
I'm trying to do a fair 20-year cost analysis and a loss through a drive should be accounted for.
Any help would be appreciated.
Thanks,
Mike





RE: VFD Efficiency Loss?
The losses for an active front end drive or one with more than a 6-pulse rectifier are probably a little higher. With more than 6 pulses, you need input transformers. However, these tend to be larger drives, perhaps medium voltage, and some of the extra front end losses might be offset by reduced losses elsewhere.
RE: VFD Efficiency Loss?
Also consider the life of the product. You might have a soft-starter survive the whole 20 years and if not then it likely would just require some repairs. I'd factor in replacing the VFD at least once in that time. Of course, you didn't specify any size - if you're talking 100's of hp or 2.4kV or higher then the VFD starts to be more modular and actually repairable.
RE: VFD Efficiency Loss?
RE: VFD Efficiency Loss?
Reactors are, as mentioned, additional loss items but, again, the losses are relative to load kw.
RE: VFD Efficiency Loss?
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: VFD Efficiency Loss?
I suggest you look at heat dissipation figures provided by the VFD manufacturers as a reasonable guide to efficiency.
We recently quoted and won a project with 4 x 450kW drives and one deciding factor was lifetime cost based on heat dissipation and the fact that additional AirCon units would be required in the plant room for the nearest alternative compared to our solution. This is a big cost when looking at 10-15yrs min lifetime.
RE: VFD Efficiency Loss?
RE: VFD Efficiency Loss?
But, if you are going to run at base speed,, why is there an inverter? And what are the efficiencies at those other speeds being compared to?
But, Gunnar's point is certainly valid. A motor running at base speed on sine wave power is certainly generating less heat than the same motor under the same loading on an inverter. So that has to be additional losses.
RE: VFD Efficiency Loss?
Boglietti, A.; Cavagnino, A.; Knight, A.M.; Zhan, Y., "Factors Affecting Losses in Induction Motors with Non-Sinusoidal Supply," Industry Applications Conference, 2007. 42nd IAS Annual Meeting. Conference Record of the 2007 IEEE , vol., no., pp.1193-1199, 23-27 Sept. 2007