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Your observation about the equation you cite is correct. The turn-on voltage, Von, does decrease as temperature increases. Using the simpler version covering just the forward conducting region of the Voltage-Current relatonship, yields: Id = Io { exp [ (qVd) / (nVt) ] }. Then, taking...

Responding to ssts' Mon, Jul 8, 2:13pm query: The following Table shows the "general" effect of a 10.9% (510/460) overvoltage on a motor's major parameters. Please note that these values are approximate and some are based on, yep, you guessed it... GOROT or "Good Old Rules of Thumb!"...

Responding to H. Ozevin's Fri, Jul 5, 9:50am advice: Caution! The no-load current will have a relatively large reactive component because of the magnetizing current requirement. Therefore, the proposed method will introduce large errors. Regards, Phil Corso, PE (Boca Raton, FL)

Replying to Pandi's observation: Three measurements are taken only if the "neutral" is available, or three instruments are being used. If not, then take just two measurements: 1st measurement... Phase leads from R to Y, with ammeter in R line. 2nd measurement... Phase leads from B...

Responding to Hakan's Sat, Jul 6, 1:0pm reply: Obviously one of us has misunderstood the other. If I'm at fault then it's my turn to utter the usual engineer creed "what I meant to say was"... If the elapsed time between start (breakaway @ t=0) and run (delta contactor closed @ t=Tr) is...

A single-phase wattmeter is a perfectly legitimate method for accurately determining power or energy in a balanced or unbalanced three-phase load, regardless of voltage and/or current waveform. A graphical method is also available, based solely on voltage and current measurements. Regarding...

Further to my earlier reply to Pandi: 1) First sentence... end of sentence should read "... used simultaneously." 2) Although I recommended a procedure using the R and B leads, other connections are possible as long as polarity and phase sequence are properly observed. Regards, Phil...

Risk Analysis isn't worth the paper it's written on! Jaundiced view? You bet it is when, even though I thought of it as a worthy discipline, the manager of a plant (refinery, in my case) says, "We're making money. Don't touch it!" Even operators and technicians, enticed by the reward of a...

Bruce's reply is well taken and if it solved your dilemma then a word of thanks should be expressed. If not, following are my comments: If the application is not a preheater and the problem not eliminated, and, If the wattmeter is installed via fixed wiring, then you may have a connection...

Responding to Captain Matlab's Sat, Jun 29, 10:41 am. query: Without knowing your specifics, I can tell you that the Zig-Zag transformer alone, presumably mounted on the VFD-side of the Delta-Delta is not a viable solution. It will do nothing more than decrease the BCR ( Cost-to-Benefit...

Responding to Bruzze's Fri, Jun 28, 2:19 pm, query: A technical correction.... the equation you presented is valid only for small deflection angles, say less than 10 degrees. Appreciable error can be introduced if the deflection angle is, for example, greater than 15 degrees! Regards...

Suggest you try a S. FLA company that installed a like-system to track Manatee movements throughout Florida's waterways. Gates and Locks were also involved. The firm is: Custom Controls Techology, Inc "www.customcontrol.net":http://www.customcontrol.net Regards, Phil Corso, PE (Boca...

Elimination usually is a process of trial and error. However, it should start with a quantitative measurement to confirm that it is "white" noise. An oft-forgotten tool is the oscilloscope. The RMS value is essentially continuous, and not from power frequency pickup, ie, 50/60 Hz or their...

Try citrus & banana irrigation contractors! Regards, Phil Corso, PE (Boca Raton, FL)

Standard IEEE 100-1992 "Definitions... " would definitely reduce the "bickering" over this thread as well as others. At least it (the Standard) would serve as the baseline for professional discussion. The latter, I believe, is a basic tenet of the List! Flame away! Regards, Phil Corso...

Position is very fluid dependent! Regards, Phil Corso, PE (Boca Raton, FL)

In general, the factors that must be considered are: o Allowable voltage drop for normal operating load. o Allowable voltage drop for future operating load as detemined by motor's Service Factor. o Allowable voltage drop for starting condition. o Type of starting, ie...

Responding to Bill Townsley's query and Bob Hogg's reply: If oil and gas are present be aware that the classification is usually Class I, Div 1 for sumps. However, if adequately ventilated or pressurized, then classificaton can be Div 2. In either case, the sensor must be "approved!"...

Responding to Brad's (Sun, Jun 9, 11:19 am) comments on Jeffs' reply: I'm not sure if your reply was meant in jest, or you were serious. If the latter, any power circuit, yes, even the 132 kV one you mentioned, can be made "production safe!" If the former... fugettaboudit! Regards, Phil...