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Responding to markvguy's Apr 14, 12:35am request for a more factual explanation: By now you will have noticed that my earlier response to petrosumit's post, covered the development of an Operating Capacity Chart (sometimes called a Performance Curve). This post addresses your request for a...

Responding to petrosumit's Apr 11, 9:56pm post... the "V" curve graph of armature-current vs field-current certainly is a measure of a generator's capability, but at best it is a "coarse" approximation. Your argument for operational symmetry in both the lagging and leading modes has some...

Further to my Apr 13, 12:51pm response to Prashant's post... Bill Moore, PE, of National Coil Company, authored a timely article on a related subject for the Mar '06 issue of Power Magazines. Titled "Include Generators and Exciters in Your Outage Inspections" it contains dramatic colored...

Responding to Prashant's Apr 10, 11:33pm query: What is starting method? Regards, Phil Corso, PE {Boca Raton, FL, USA} [[email protected]] ([email protected])

Responding to Curt's Mar12, 12:00pm and Meir's Mar 12, 12:02pm comments: Tsk, tsk... I too appreciate not-to-technical answers... but, they should be technically correct: A) Turns-ratio is not responsible for overvoltage. Even CTs with lower ratios, like 5:1 or 1:1, have the cautionary...

Responding to Anonymous' Mar 7, 11:04pm query... please clarify how 37% was determined: 1) Ammeter measurement is 37% of motor's Ampere rating? or 2) Power-meter measurement is 37% of motor's kW rating? Regards, Phil Corso, PE {Boca Raton, FL, USA} [[email protected]]...

Responding to G. Laloumis' Mar 1, 1:02am query: Q1) Are observed voltage variations ph-ph, ph-earth, or across delta? Q2) Are observed voltage variations random occurrences? Or, do they occur at times coincident with a specific plant condition? For example, when operating a very large...

My interpretation: You're concerned an ungrounded power system could have the potential for a ferroresonance condition because of the existence of PTs (or VTs) used to power indication, annunciation, metering, or protection circuits. Their primaries are connected as earthed-wye. Their...

Responding to Shane's Feb 24, 1:07am observation... you are correct if Anonymous wrongly observed it to be a single-phase case: The numbers are correct for the three-phase case. V = 415.0 A = 10.7 (Given) kVA = sqrt(3) x A x kV = 7.69 kWin = 6.47 (Given) PF = 6.47 / 7.69 =...

Responding to Anonymous' Feb 24, 12:33am query... some, but not all, different vector group transformers can be paralleled! The answer is simple, but implementation isn't. The usual parameters to determine circulating current are voltage-ratio, turns-ratio, impedance, polarity, pri-sec...

Responding to SC Patel's Feb 21, 11:31pm query... the List Archives contain pro/con views regarding safety, transient reduction, and calculation methods. Dismissing the above, then, the greatest benefit of resistance grounding is an economic one... to reduce iron-core damage. Larger...

Responding to Anonymous' Feb 21, 11:37pm comments: Obviously you know more about the original query than was described. Please clarify. Regards, Phil Corso, PE {Boca Raton, FL, USA} [[email protected]] ([email protected])

Responding to Oscar's Feb 9, 12:40am query... No! Although self-starting, the shaded-pole motor having copper-straps around the smaller poles, cannot be reversed. However, there is a solution if reversibility, as well as the benefits associated with the shaded-pole motor, are essential...

Responding to anonymous' Jan 29, 1:26pm query... there are two reasons for the dual-capacitor motor: 1) Higher Starting-Torque. The parallel combination of two caps, one, electrolytic, the other, oil-filled, are inserted in the start-winding circuit. The electrolytic cap provides a higher...

Responding to Rajasekhar's Jan 07, 1:16pm query... presuming you want to determine the starting and running currents, do the following: 1) The circuit model for the starting and running cases are the same as the fundamental frequency case. So, set-up the circuit in EXCEL. 2) Perform a...

Responding to Ramesh's Dec 18, 5:00pm query... If your question is "What is the alternative method", then: Par 3) Instead of using an ohmmeter, connect each pair of conductors to a stable DC source, say 5-10 V, and measure the current. Calculate the average current for the three phases...

Responding to Ed Battle's Nov 19, 2:08am query and Anonymous' Nov 20, 4:05pm reply... the most important reason is based upon safety: 1) Shielding is used to confine a cable's dielectric field to the inside of the cable's insulation. It consists of surrounding the insulation or assembly with...

Responding to Sunil Cornelio's Nov 4, 11:29pm query... just some cautionary observations: 1) You haven't mentioned the country of installation, but if the US or Canada, are you sure the sanctioning authorities have accepted Energize-To-Trip (ETT) for safety-control circuits? 2) You...

Responding to Dave Downunder's Oct 25, 8:12pm query... conversion between metric & English units is often a source of error because of the Flywheel Effect is determination. In the following formulae, please note my deviation from "SI" terminology by labeling mass as "m" while meters as "mt"...

Responding to Anonymous' Oct 23, 9:33pm query... the circuit was used to prevent reclosing a breaker into a fault! Westinghouse referred to it as the "Electrically Trip-Free" Scheme. Some called it the "X-Y Relay Circuit." It prevents breaker "pumping" (repeated opening/closing action) if...