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Responding to Bob Peterson's Thu, Jan 16, 10:21am: One major company I was with debated the question of battery isolation for years. The answer was an emphatic YES, the very day one blew-up during a UPS short-circuit test. Remember the old saw... "It ain't a problem until it happens!"...

A ponderable... Why is blame always assigned to the lowest person on the totem pole. To paraphrase a popular song "Where had all the experts gone?" In virtually all catastrophe (my definition) investigations I've been involved in, none, I repeat, NONE, were the fault of anyone higher in...

James, it was a joke!! Regards, Phil Corso, PE (Boca Raton, FL) [[email protected]] {[email protected]}

I don't know if my story was one of your four known incidents, except we called it DCS lockup. It occurred in a mid-west refinery. Conversion to an upgraded DCS had been completed on this day. On a success-high management decided to also commission a co-generation unit. Unfortunately its...

Bill, I didn't question your veracity regarding LV to MV comparisons. I questioned your interpretation of Todd's query, which I interpreted as lower LV to higher LV. I apologize for making you angry! Regards, Phil Corso, PE (Boca Raton, FL) [[email protected]]

Further to previous discussions: Those interested have probably noticed appreciable difference in loss calculations between Alpasian Pak's and mine. The reason, of course, is the source of pertinent data. Alpasian's information may have come from a motor vendor, while mine came from the...

Dear Hakan, Then, you probably know that load current is the least accurate... if voltage varies. In my experience I have used one or the other methods to determine load-factor at least 5 times, or about once every eight years. But, that then begs the question "what is experience?"...

Further to my Thu, Jan 2, 3:00pm post covering the direct equation method: The equation covering method 5) has an error. The 'B' term coefficient should have been '+', as follows: 5) Load estimate by direct equation: Y = A x X + B Regards, Phil Corso, PE (Boca Raton, FL)...

Responding to K. Gurumurthy's Fri, Jan 3, 11:53am question about AT vendor's parameters: The resistance follows the square law. If kVA is constant and voltage is doubled, then resistance/impedance is quadrupled! Thanks for clarifying my understanding of star-point contactor. Regards...

Further to my Thu, Jan 2, 5:59pm response: Because the problem only appears with the 6-kV systems there are two components in question: a) motors; and b) auto-transformers. Thus, one approach would be to compare characteristics. a) Motors The 3 and 6-kV motors should be relatively easy...

Responding to W. Hinton's Thu, Jan 2, 5:34pm reply: Your generalization is greatly exaggerated! I don't think Todd asked for a low-voltage, LV, to medium-voltage, MV, conversion, but from 208 to say 230 or 460 Volts. My response to Todd's query is, "ask motor manufacturers for their...

Responding to additional comments in K. Gurumurthy's Thu, Jan 2, 7:20pm transmittal providing additional data: 1) Installation history provided. 2) Because load-inertia is less than motor inertia, assuming no intervening gear-box, then inertia is not the problem. 3) For math analysis, the...

Responding to K. Gurumurthy's Thu, Jan 2, 7:20pm transmittal providing additional data: Urgent Do not increase time-to-transfer, unless you have confirmed withstand capability of AT! Conclusion The data you provided indicates, to me, that net accelerating-torque (motor-torque less...

Further to my earlier post covering the slide-rule method: For those of you who can't find theirs, or never felt the power of one strapped, holster-like, to their belt, or worse yet don't recognize the term, here is a simpler method than the slide-rule. It is: 5) Load estimate by direct...

My initial posting omitted the most unusual method in my 47+ years experience. I used it in my previous life when a smart-stick was all one needed! Therefore, I dedicate this method to List members that remember the... No! Not the Alamo, the... Slide-Rule: 4) Load estimate by Slide-Rule. Kr...

Responding to Matt Tudor's Tue, Dec 31, 11:53am car analogy: VW actually did have a fuel cut-off if block temperature got too high. And it wasn't covered by their manual! It happened to me, in the boonies, at night, way before any one thought of cell-phones. Regards, Phil Corso, PE (Boca...

Responding to W. Hinton's (Sun, Dec 29, 10:49am) reply: While your perception of its function is that of back-to-back zeners, the varistor is actually a voltage controlled resistor, as suggested by Haken Ozevin. In fact it is a two-terminal semiconductor device having a voltage-dependent...