How To Restore The Residual Magnetism In My DG?

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muthuk10 Active Contributor Join Date: Sep 2014 Posts: 19	How To Restore The Residual Magnetism In My DG? 09/29/2014 3:19 AM
	500 KVA DG, kept idle for last one year, now i am trying to start the DG it was generating only 40v instead of 440v AC so now i feed the 12v dc from battery for excitation (externally) now this moment i can get 460v at output terminal. once again i am connecting through AVR (E+ AND E-). The situation remain same (means still it was generation 40v) now one thing is very clear that is the residual magnetism of the field may lost due to laid idle. if it is so kindly suggest me how to restore the residual magnetism? or any other issue please suggest how to solve this issue?
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RAMConsult Guru Join Date: May 2007 Location: NYC metropolitan area. Posts: 3230 Good Answers: 444	#1 Re: How To Restore The Residual Magnetism In My DG? 09/29/2014 8:48 AM
	It means that something between the terminals of the machine and the terminals for the field is open. If you have 40 Volts without external excitation and 460 V when you flash the field then you have enough residual magnetism to build up voltage IF everything else is working properly. Check fuses, diodes, AVR, connections, etc. until you correct the problem. __________________ “Tell me and I forget. Teach me and I remember. Involve me and I learn.” Ben Franklin.
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SolarEagle Guru Join Date: Mar 2007 Location: by the beach in Florida Posts: 33392 Good Answers: 1817	#2 Re: How To Restore The Residual Magnetism In My DG? 09/29/2014 8:49 AM
	Found this for you.... https://www.cumminsgeneratortechnologies.com/www/en/common/pdfs/other/fault_finding_manual_8.pdf __________________ All living things seek to control their own destiny....this is the purpose of life
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Unredundant Guru Join Date: Feb 2008 Location: Large hole formally occupied by furry woodland creature. Posts: 3385 Good Answers: 97	#3 Re: How To Restore The Residual Magnetism In My DG? 09/29/2014 10:51 AM
	If your generator has circuit boards, rodents can do some serious damage to them. Check for mouse peepee tracks. __________________ CRTL-Z
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vishram lele Commentator Join Date: Dec 2009 Location: India Posts: 68 Good Answers: 4	#4 Re: How To Restore The Residual Magnetism In My DG? 09/30/2014 12:04 AM
	In the alternators the Residual Magnetism is stored in Exciter Stator Laminations, all other parts like Main Stator and Main Rotor are of Silicon Grade Material do not store residual magnetism. If the terminal voltage is 40 volts, the AVR should pick up and the Alternator should build up the voltage. In case of Cummins, LS and Weg alternators the Min Residual voltage required for voltage build up varies between 3 to 9 Volts only. Please try changing the AVR If Changing AVR does not work, try following, after every step check the voltage build up - 1. Do not run the engine and Flash the Exciter Stator terminals with 12 V DC with the help of External DC Source (Battery Bank) ( E+ Positive and E- Negative) 2. If voltage is not building up, then increase the Excitation Voltage in the steps of 12 Volts till 36 Volts----- Do not Run the engine....This is static Charging of the Excitator Stator. 3. If the above 2 Fails to charge the Excitator Stator.. Remove the Excitator Stator..charge with 40 V AC ( Yes AC)...then charge with 36 Volt DC. 4. The final solution would be to replace the Excitator Stator.
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CBlackwood Member Join Date: Feb 2013 Posts: 7	#5 Re: How To Restore The Residual Magnetism In My DG? 09/30/2014 4:48 PM
	If you have 40v terminal voltage, you have residual voltage. If the unit is shunt excited. (AVR is powered by the output terminals of the generator) the AVR is bad and needs replacement. If the AVR is powered by a PMG. Check the input voltage to the regulator. If it has the correct voltage, AVR is bad and needs replacement. If it does not have voltage going to the regulator, replace the PMG.
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