Search results

Further to my May 9, 8:50pm response to Rajeev: Assuming that the three transformer windings are relatively balanced, and this were a 2-wattmeter measurement with one showing a negative reading, then, it is due to the power factor being less than 0.5. But, a negative reading in a 3-wattmeter...

Responding to Rajeev's May 8, 6:34pm query. A lot more information is required. As a start: Q1) Does the sum of 3-single phase measurements, using the same wattmeter and taken one phase at a time, equal the algebraic sum of the 3-simultaneous measurements? Regards, Phil Corso, PE {Boca...

<p>Responding to Kaveh's May 6, 3:40 pm, calculation: <p>I'm assuming that you disagree with my Feb 3, 12:06 am, response to Mr. Hakami. My answer, then, was that the added capacitor reactance is Qc 83.1. So let's return to basics: <pre> S1 = 1,400 kVA (Given) P1 = 1,372 kW " Pf1 =...

Responding to Krishna's May 5, 4:04pm query: You should be aware a subject of this magnitude is well beyond the A-List charter. However, following are two items that I found most problematic, and unfortunately, often ignored: Oscilligraphic Testing. Confirm that mechanical operation, for...

Further to my May 1, 12:55 response to Daniel Camacho's query: L-units should have been mH/k-units. I -units should have been kA. Continuing Part Deux (sent after 12:55pm,) following are induced emf, neglecting input resistance of connected 24Vdc devices: Case 1, Single Motor...

Further to my response to Daniel Camacho's query: Part Deux: the quantitative analysis. It is far easier to measure the induced emf at either end of an open-ended 24 volt loop than it is to calculate. On a more serious note, it is my opinion that the installation you described...

Responding to Daniel Camacho's Apr 28 query: Although you have never experienced a voltage induced problem I assume you accept that such (undesirable) effects can occur. Then, one must ask, rhetorically, what is unique about your installation? First the qualitative analysis. It can be...

VRLA is Panasonic's trade-name for a sealed, but vented battery! Regards, Phil Corso, PE {Boca Raton, FL, USA} [[email protected]] ([email protected])

Responding to Jan Husyser's Apr 19 concluding comment: Please excuse my tenacity (others would call it stubbornness), but the numbers don't make sense (to me.) Ignoring the thickness of the enamel coating, then, the diameter of 0.015 mm (15 um) is less than the thickness of a human hair...

Responding to Curt Wollet's Apr 12 reply: Curt, for analysis presume that the unwound coil yields a long straight wire. Furthermore, doubled back the wire on itself so that there are now 2 parallel wires. For this case the formula covering a single-phase 2-wire transmission line is...

Responding to Matt Hafele's April 11 query: Your description of the motor's duty cycle is only one part of the quest to determine the equivalent horse power needed. Some other salient parameters to investigate are: a) Load torque. b) Load inertia. c) Define "reversal"... is motor...

Responding to Jan Huyser's Apr 11 query: Your gut feel about the consequence is correct for an AC solenoid. And, it just wouldn't work if the solenoid was DC. But, before getting to the nitty-gritty comparison of the two scenario's you presented please clarify two apparent inconsistencies...

Responding to Joel Young's plight: Thus far you have supplied a great deal of qualitative observations. How about some quantitative info. Some of the questions that would provide additional insight are: 1) Is there a noticeable difference in "noise" between the start (higher current) and...

Responding to earlier responses to Flyer's original Jan 17th post: Meir and Curt... I'm surprised at your "TIC" semantic attacks... log vs exp vs nvat. So here is a little more light on the subject: While it is true that resistance vs wiper position is an exponential one, the plot of...

Responding to Flyer's Jan 17 and Joseph's Feb 26 queries. I can help if you are still interested in a solution. For example: 1) Do you need greater accuracy than can be accomplished with an audio-taper pot found in Radio-Shack? 2) Do you need greater precision using a multi-turn pot? 3)...

Meir, Hopefully you meant SOME of the motors' kVAR. "Zero" should never be the goal! Regards, Phil Corso, PE {Boca Raton, FL, USA} [[email protected]] ([email protected])

Responding to Anonymous' Feb 28 query: It can be done with litthe more than a couple of capacitors: 1) What are the motor's nameplate values? 2) What speed ratio do you need? 3) Is the motor you have adequate for the lathe? Regards, Phil Corso, PE {Boca Raton, FL, USA}...

Your treatise on VFD drives to operate motors in ranges greater than their normal speed is excellent. However your generalization about doubling of rpm requires a cautionary notice. Although certainly possible, the probability of success is very dependent on the mechanical design of the...

Replying to N. Vedachalam's Fri, Feb 18 query: When operated hypersynchronously (above synchronous speed) a motor's torque/slip curve has a shape similar tothat for subsynchronous operaton. In other words, if speed is increased above synchronous speed, by an amount equal to its rated slip...

Responding to Anonymous #62 and Anonymous #87.01-b, both of whom contacted me off-list to ask how the 0.86 power factor value was derived: Let PFe = the earlier power factor, i.e., before the addition of the 550 kVAR capacitor. Then, substitute PFe and PFo for PFo and PFd, respectively, in...