Posted 11 August 2006 - 02:39 PM
My question is about measuring consumed energy with VSDs. We have a situation where there was a DOL starting of motor (high power) and using flaps for flow regulation in verntilation system. Now a frequency inverter will be installed (plus line chokes).
Of course, measurements will be taken to estimate the energy saving due to frequency regulation vs. mechanical regulation (on 100% power). Is there any special consideration regarding measurement? Is it possible that the measurements are not correct because of the inverter operation?
Thank you for your answers,
Posted 11 August 2006 - 05:44 PM
The easiest way is if your VFD has a kW output or display, because it is internally doing those complex calculations. You can assume a 3-5% efficiency loss in most cases, with the 5% being at lower speeds and 3% at full speed (in a typical VAV fan system).
Posted 11 August 2006 - 10:06 PM
A simple rotating disk KWHr meter on the input of the drive will tell you what you are paying for and because they use a magnetic multiplier, they give an accurate result for the drive input.
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