Perran: The induction motor (Generator) GRID connected, follows the GRID frequency and the RPM of the GEN, in this case, is going to be the RPM defined by the number of poles and the GRID frequency PLUS twice the SLIP Value. To detect this you may have an RPM detector to make sure that the GEN does not run as a motor, which happens if the hydro pressure lowers. Also, techniques like reading the current into the grid with the voltage as a reference to detect the current direction -- this is faster and more accurate.(synchronous current detection).
Frequency will not move from the GRID frequency-- it can not move ( vary) because the motor bias is set by the GRID. If the generator has excessive applied torque ( by the Turbine), one may have issues like heavy currents and (PF) Power Factor. And for those interested, one may have two hydros operating in parallel, in where one is a master (GRID) and the other is the slave ( in this case an induction motor) which should be capable of producing not more that about 50 % of the master. Regards Nando ----- Original Message ----- From: "H2MJD" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Thursday, May 05, 2005 8:48 PM Subject: Re: [microhydro] Digest Number 1153 > > Can someone tell me how you can provide this 'utility required' protection > with a directly connected induction motor. My understanding is that power will > flow into or out of the grid in a seemless manner depending only on the speed > of the motor/generator shaft and the torque applied. Am I right ?? > > Perran Newman > > > > Perran, > You are right. When wiring in the motor/generator typically a magnetic contactor (motor starter) is used to apply power to the unit. The Over/under voltage and over/under freq relays monitor the voltage and frequency of the utility power. If the voltage or freq move outside the utility perscribed limits(and this will only happen if the utility is experiencing a problem) these relays will remove power from the magnetic contactor's coil and the motor/gen will then be isolated from the utility grid thereby providing safety to all.......i hope this helps.......mark > > > > > > > [Non-text portions of this message have been removed] > > > > > > > Does your company feature in the microhydro business directory at http://microhydropower.net/directory ? If not, please register free of charge and be exposed to the microhydro community world wide! > > NOTE: The advertisements in this email are added by Yahoogroups who provides us with free email group services. The microhydro-group does not endorse products or support the advertisements in any way. > > More information on micro hydropower at http://microhydropower.net > > To unsubscribe: send empty message to [EMAIL PROTECTED] > Yahoo! Groups Links > > > > > > ------------------------ Yahoo! Groups Sponsor --------------------~--> Has someone you know been affected by illness or disease? Network for Good is THE place to support health awareness efforts! http://us.click.yahoo.com/RzSHvD/UOnJAA/79vVAA/FGYolB/TM --------------------------------------------------------------------~-> Does your company feature in the microhydro business directory at http://microhydropower.net/directory ? If not, please register free of charge and be exposed to the microhydro community world wide! NOTE: The advertisements in this email are added by Yahoogroups who provides us with free email group services. The microhydro-group does not endorse products or support the advertisements in any way. More information on micro hydropower at http://microhydropower.net To unsubscribe: send empty message to [EMAIL PROTECTED] Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/microhydro/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
