How Variable Frequency Drive (VFD) Works & Saves Energy

This question has been asked before and the answer is usually, "Wikipedia is free". Hope this sends you in the right direction.

How a variable frequency drive works?

See these links:

http://en.wikipedia.org/wiki/Variable-frequency_drive

http://www.joliettech.com/what_is_a_variable_frequency_drive.htm (Part 1)

http://www.joliettech.com/what_is_a_variable_frequency_drive-how_vfd_works.htm (Part 2)

http://oee.nrcan.gc.ca/industrial/equipment/vfd/index.cfm?attr=24

How a variable frequency drive saves electrical energy?

See this thread:

http://cr4.globalspec.com/thread/55271 (comment # 4)

There are also many other threads available in CR4 for this topic. Search for those.

- MS

Generally, speed drive does not save much energy. The most you can save is about 10 to 20% of your total power (KW) for motors. Some motors especially for water pump or for exhaust fan can save about 10% only. The investment cost is very expensive and the ROI is very long period of time.

If you run the speed drives to low speed, you will eventually loss the power and energy instead of saving it. It depend on what application you want to use on it. Otherwise, not much saving.