If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
So im having this problem at work where a 150kW induction motor is being used as an induction generator. There is a capacitor bank in parallel to the induction generator which is primarily for PFC(the reactive power requirement of the generator is fed by the grid).
Assume the induction generator is islanded( i.e the capacitor bank is out, the grid is out and the induction generator is the only thing that's connected to the load)
What would happen to the induction generators speed? If a step by step explanation on what will happen would be great.
From my thinking when the capacitor bank and the grid power goes out the generator has no source of vars to sustain the stator magnetic fields. (i.e stator magnetic field will collapse pretty much instantly which will produce a large voltage in the stator coils due to Ldi/dt)
1)After this initial Ldi/dt voltage spike it would cause a large current to flow in the stator coils?and it would oscillate?
2)Or because of the lack of reactive power the stator will have no magnetic field and that would stop inducing and emf on the rotor which will collapse the rotor magnetic field and stop the generator all together?
say the magentic field is not there anymore in the stator, would it cause the rotor(which is connected to an impeller) to freewheel and destruct itself?
Registered Member #2463
Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546
You are correct as to the spinup destruction. The oscillation, will occur but the spark across the contactor between the generator and the grid will eat that energy, Is this 1 200 HP 600 volt machine?
Motor insulation is tested in certain cases by hitting the the winding with a fast rising pulse and looking at the ringing the coils produce with their self-capacity.
Iy you dont do it correctly, you will restroy the insulation, leaving no doubts about its quality.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
If the generator loses its capacitor bank, it can't generate any more. An induction generator needs a capacitive load to excite it. The rotor will demagnetise, the output voltage collapse to zero, and it will stop consuming mechanical power, which may make the prime mover run away.
If it gets islanded with a load that's unity or leading power factor, it could keep on generating, with voltage and frequency way out of spec. So you probably want to make sure that the load it's islanded with is not PFCd.
You can get regulators for induction generators, intended for the micro-hydro industry, if you can call it an industry.
If the generator loses its capacitor bank, it can't generate any more. An induction generator needs a capacitive load to excite it. The rotor will demagnetise, the output voltage collapse to zero, and it will stop consuming mechanical power, which may make the prime mover run away.
If it gets islanded with a load that's unity or leading power factor, it could keep on generating, with voltage and frequency way out of spec. So you probably want to make sure that the load it's islanded with is not PFCd.
You can get regulators for induction generators, intended for the micro-hydro industry, if you can call it an industry.
what do you think would happen in the instant the capacitor bank is out? would the voltage instantaneously rise at that very moment due to the collapsing field?
Registered Member #1617
Joined: Fri Aug 01 2008, 07:31AM
Location: Adelaide, South Australia
Posts: 139
hat do you think would happen in the instant the capacitor bank is out? would the voltage instantaneously rise at that very moment due to the collapsing field?
If it was connected to a unity power factor load, and not to the grid I'd think the voltage would go through the basement, rather than up, since there'd be no more excitation from the caps?
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
scrooch wrote ...
what do you think would happen in the instant the capacitor bank is out? would the voltage instantaneously rise at that very moment due to the collapsing field?
I don't know. It might do, but I think the spike would be no bigger than what you got when switching out a 150kVA transformer.
If it's really critical, you should simulate the system using something like EMTP.
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.
effect of sudden loss of reactive power supply for an induction generator
