David: One may use the AC voltage polarity to detect the current direction (in or out) of the motor to determine if working as a motor ( IN) or as a generator (OUT).
Also, one needs to determine the current phase angle to fully defining the motor operation Of course the Synchronous detection will show such phase angle -- This is not for the novice -- To see the effect of synchronous detection assume that you have 2 voltages, one called Motor and another Generator, inter-connected with a resistor in series ( The clamp meter). Make Generator voltage 2 X, the Motor Voltage, so the current will flow from Generator to Motor. Make Motor Voltage 2 X the Generator Voltage, so the current will flow from Motor to Generator The clamp meter just measures the current out of the generator, without any phase angle determination. I hope this helps, if not ask again Nando ----- Original Message ----- From: "David Green" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Monday, May 09, 2005 12:18 PM Subject: Re: [microhydro] Digest Number 1153 > Hi Nando, > > Could you expound a bit on the "(synchronous current detection)" that you > mention. I use a clamp on meter as an amperage detector. As I change > nozzle configuration on a pelton I can see my Kw's. > > David > ----- Original Message ----- > From: "Nando" <[EMAIL PROTECTED]> > To: <[email protected]> > Sent: Friday, May 06, 2005 5:23 AM > Subject: Re: [microhydro] Digest Number 1153 > > > > 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 > >> > >> > >> > >> > >> > >> > > > > > > > > > > > > > > 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! 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