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Responding to Anonymous' Feb 5, queries... the following discussion applies to only electrically operated devices: IEEE Definition Std 100-1992 "Standard Dictionary of Electrical and Electronic Terms" (Std 100-1992) has many definitions for 'Relay'! Conversely, the Standard's only...

Responding to Mr. Hakami's Mon, Jan 31 reply... If I'm wrong please correct me. Your approach was to find the difference between the original state and new state inductive reactance values, kVARc = kVARo - kVARn Paraphrasing the original question, "What additional capacitive reactance...

Further to my earlier response of Mon, Jan 24, 6:24pm to Anonymous' Thu, Jan20, 12:37pm query: Correction. The formula has to many open-parentheses. The correct is, kVARc = { tan[Acos(PFo)] - tan[Acos(PFd)] } x kW, where, Acos = ArcCosine. Regards, Phil Corso, PE {Boca Raton...

Further to my earlier response to Anonymous' Jan 20 query: Because I don't know the reason you asked for the calculation method provided, do not misconstrue my submittal as an endorsement to do it. Raising power factor beyond that required to fulfil an economic incentive must be done after...

Responding to Anonymous' Thu, Jan 20, 12:37pm query. There is a trignometric relationship between PFo (original) and PFd (desired), that will yield the additional capacitive reactance. The procedure follows: PFo = Original power factor. PFd = Desired power factor. kVAo =...

Steve, an apology is unnecessary. I thought, based on David McConnell's post, that a more complete response was in order. Hopefully, it will clear up some obvious (and dangerous) interpretations by one or some of the anonymi. An aside... I'm not sure about the plural of anonymous... is it...

Responding to C. Hardacker's Jan 14, 2005 query: Regarding your position on DOL (Direct-On-Line starting), I believe you have the cart before the (excuse the pun) horsepower. Unless the load or driven machine is negatively affected by DOL starting, then reduced-voltage starting for...

Further to my earlier reply to C. Hardacker's query: Oops... the most feared word in an operating room... I erred. Yes, engineers occasionally make mistakes (but very, very few will admit it)! The earlier % voltage drop values are wrong. The voltage drop values for the 500 kcmil and AWG...

Responding to C. Hardracker's query... I believe you have the cart before the (excuse the pun) horse(power). Unless the load or driven machine is negatively affected by DOL starting, then reduced-voltage starting for medium-voltage motors should be dictated by the short-circuit capacity of...

Responding to F. Straat's query: Temperature-rise above ambient is a very good way to determine a motor's output hp or kW. Measure the winding's dc resistance when the motor is stopped in its normal ambient location. Then measure the resistance after the motor has been operated under...

Responding to Anonymous' query: (1) The 'high-leg' 3-phase system is more properly referred to as a center-tapped (high-leg or red-leg) 4-wire, delta system. It is important to note that this system finds favor if the 120 V 1-ph, loads are small compared to the 240 V, 3-ph, loads. (2)...

Further to NV's query of Wed, Jan 5, 8:42am: Is current 10 Amp per core? Or 3.3333 Amp per core? Regards, Phil Corso, PE {Boca Raton, FL, USA} [[email protected]] ([email protected])

Responding to NV's query: Yes, there is a way. But first, what is highest ambient temp? Regards, Phil Corso, PE {Boca Raton, FL, USA} [[email protected]] ([email protected])

Responding to N. Vedachalam's query: Of course you can! The same formulas used for 50 Hz are adequate for 450 Hz. Now for the caveat... You must compensate for the 9-fold increase in inductive reactance. To a lesser degree, you must consider the 9-fold decrease in capacitive reactance...

Responding to Graham Steele's understanding of the incompatibility notification: I believe the output transistor's "break" or turn-off capability is inadequate... not its "make" rating. Regards, Phil Corso, PE {Boca Raton, FL, USA} [[email protected]] ([email protected])

Responding to Anonymous' Dec 8 query: The are two principle reasons for applying a choke in a VFD installation: 1) To reduce the fault-current available at the VFD location. This will increase the chances of semiconductor survival during fault-clearing. 2) To ameliorate the effects of...

Responding to Anonymous' dilemma: If the drive motors are asynchronous, and their output shafts "drive" the same centrifuge shaft then the problem could be easily explained! But... more information is required! Regards, Phil Corso, PE {Boca Raton, FL, USA} [[email protected]]...

Responding to Anonymous' Fri, Nov 19, 1:19pm query: My Best-Guess-Estimate (BGE) is 3.5%! Regards, Phil Corso, PE {Boca Raton, FL, USA} [[email protected]] ([email protected])

Responding to R. Louie's questions: Q1) How does capacitor work in a split-phase motor? A1) In retrospect, it is obvious to me that my May 12th reply was long-winded. Here is a simpler version: The motor has two windings called he "main" and "auxiliary!". They are electrically...

Responding to Burman's Tue, Nov 16, 4:38pm query: There appears to be substantial, but undesirable, current flow between neutral and earth. For analysis please provide the following: 1) Is this a new problem? Or one that has existed for a while? 2) Where were measurements made? At...