Use motor as grid tie inverter - Page 1
Forum section: electronics / general

author: 2N2222A
author_rank: Regular Contributor
timestamp: November 26, 2022, 12:02:05 am
content: If an induction motor is connected to the grid, can it be turned faster than 1500/1800 or 3000/3600 and put power back in to the AC mains?It's pure sine! Anti islanding (in most cases)! Has the regulatory certifications already!I think phase can be corrected with reactive components. Probably not needed any more than with the motor in normal use.Can this work?

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 26, 2022, 01:59:17 pm
content: That's exactly how it works. But if the point is to work around regulations about connecting homemade circuits to mains, it would be more efficient to use a transformer so the homemade circuit operates at low voltage and is therefore not covered by the regulations.

author: pqass
author_rank: Super Contributor
timestamp: November 26, 2022, 03:59:27 pm
content: Just because an induction motor has the usual UL certifications for safety or whatnot, doesn't mean it gives you permission to connect it (as a generator) to the power co's network.Every meter is backed by a contract that defines the relationship as a load, generator, or both (grid-tied). You may go undetected for a while (turning your meter backwards) until (a) they notice that they owe you money, (b) some linesman gets lit-up, or (c) your home made control system fails and your now unsynchronized generator gets hurled through the roof.A transformer between network and generator just changes the wire guage in the generator. It won't grant you freedom from regulation.https://hackaday.com/2017/07/05/how-do-they-synchronize-power-stations-with-the-grid/

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 27, 2022, 01:28:56 pm
content: If there's no agreement to backfeed the grid, then you do indeed need some way to prevent exporting. And that's where the induction motor as generator can fail, as response time would be limited by inertia.Quote from: pqass on November 26, 2022, 03:59:27 pmYou can get a transformer that's already UL listed to connect to mains (probably harder to find a large one nowadays with switchers taking over much of the market), the secondary side would be low voltage and what you connect to that would not need UL listing.

author: 2N2222A
author_rank: Regular Contributor
timestamp: November 27, 2022, 05:36:33 pm
content: It doesn't have to exceed the power purchased rom the utility. Many grid tie systems don't, and some meters even charge customers in both directions.Nearly every utility user puts electricity back in to the grid at 100 or 120 times per second, in the form of bad power factor. It's a less extreme version of using the grid for energy storage, or slow response time from a generator. Putting extra electricity in during the day and using more at night is a much greater burden on the utility company than bad power factor or slow generator response, but it is really the same concept.Wouldn't the induction motor when used as a generator work against the bad power factor from existing induction motors in appliances like refrigerators? Or does it not work that way? I once read that an induction motor will work as a generator with an exactly right sized capacitor used with it. All loads must be non reactive for this to work.