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How To Determine Energy Savings - Help


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Hi all, I am having to carry out an energy savings survey from my client who has over 200 motors some of which are very very old. I have look at the motors and they are all small drives with a handful of 22kW, 7kW, 5.5kW and 4kW. All others are below these ratings. I am looking at ddeveloping an approach to looking at this. Obviously, I don't want to carry out a survey on all motors.


What I have in mind is to review the asset schedule and; to identify the bigger motors, carry out a physical survey of these bigger motors reviewing the eff, pf and starter types including the application. The idea is to change motors with varying load to VSDs where they are not and also to propose more efficient motors.


Any idea on what should be looked at typically or how to approcah this?



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Hello epsngr


That is a simple question to ask, but a complex question to answer!!


Firstly, please note that larger motors are much more efficient than smaler motors. If the bulk of the motors are small, then that is where the highest energy losses are. If there was on 10KW motor and 20 0.5KW motors, the combined losses from the 0.5KW motors could be 5 times that or the one 10KW motor so do not dicount the small motors.


Secondly, the addition of VFDs will only save energy if the machine is able to run more efficiently at less than full speed. For example a pump or a fan that has only half or its design flow for a high percentage of the time with the flow being restricted by a valve or by dampers external to the pump/fan.If the pump or fan is being throttled, then slowing it down to achieve the same flow wil save energy. - This will not happen in every case.


Best regards,


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