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Responding to Joel's Wed, Nov 10, 5:13pm query: Could be a voltage regulation problem, and not a harmonic one. Here are some questions which will shed some light (excuse the pun) on the problem: 1) What indications are given for the VFD tripping? Undervoltage? Overvoltage? Overcurrent...

Responding to "d's" query. Here's a start. As part of earlier study related to motor efficiency vs size, the windage & friction power loss for the motor in question is about 2.4%. Regards, Phil Corso, PE {Boca Raton, FL, USA} [[email protected]] ([email protected])

Responding to Salatoo's Tue, Oct 12, 8:50pm query... are you asking: "What size capacitor is required to operate a 3-phase motor on a single-phase supply?" Regards, Phil Corso, PE {Boca Raton, FL, USA} [[email protected]] ([email protected])

Responding to Accord.K's Tue, Oct 5 query: An excellent question! Of course, tere are a myriad of factr to consider. And, although a motor designer could more adequately answer the question, I will try. My thesis is analogous to the theory of "Economy of Scale!" Although considered a myth...

Responding to Sonny's problem: I'm not sure if the following will help or not, but it's real-world experience. It is a story of what an "observation" is. Or, paraphrasing a popular phrase "OK to one may be NOK to another!" Names are being omitted to protect the stupid! I was testing the...

Responding to Rodney Barr's Mon, Aug 9, 6:21pm query: Try Kerk in Holland! Regards, Phil Corso, PE {Boca Raton, FL, USA} [[email protected]] ([email protected])

Responding to John's Tue, Aug 3, 9:57pm query: What is country of origin? In the interim, it appears to describe a 3-phase transformer. The primary-winding is delta connected. The nominal phase-to-phase input rating is 361 to 370 Volts, with two +5% tap settings. The secondary-winding...

Responding to Anonymous' Tue, Aug 3, 7:29pm comment: The data you provided indicates that items 1) & 2) of my response can probably be ignored. However, you still haven't supplied answers to item 3) nor an answer to William Hinton's Jun, 11:04 pm query. Because the system is large (30...

Responding to Daryl K's original query... here is a reiteration program using only te aritmetic functions. A^x = e^(xlna) = e^B. Letting B = xlnA, a constant, then, e^B = [1+ sum (n = 1 to n) B^n / n! ] But a simpler series to implement is, e^B = [ 1 + sum (n = 1 to n ) B^n / C(n)...

My comment was only to clear up the misconception that it couldn't be done. How, wasn't asked. It is left for the time the question is raised! BTW, I disagree with your statement about the 'work' needed between the supply and the motor to make it happen. It could consist of as little as...

Just to clear up a misconception: A 3-phase motor can be supplied from a single-phase source. Of course, there are limits and constraints that apply! Regards, Phil Corso, PE {Boca Raton, FL, USA} [[email protected]] ([email protected])

Responding to M. Ramkrishna's Mon, Jul 12, 2:16pm query: While MCBs are available for AC and DC, their being available for both AC and DC is unusual. The exception is for very special cases. Typically, such a unit will have the AC-rated contacts within the molded thermo-setting plastic...

Responding to Sanjay Patil's Thu Jul 8, 1.22:pm query... I suggest the following approach: 1) Use NEMA Standard MG 1-20.42. It contains a table derived from an empirical formula that relates load WR2 and motor Hp & speed. 2) Knowing Hp and speed calculate the required torque. 3) Use...

Responding to Anonymous' Sat, Jul 10, 8:09am request for clarification: Power Factor correction should be treated as a double edged sword: A) The Good Edge. Improvement reduces the apparent power (kVA) drawn from a power company. Therefore, they encourage correction by imposing penalties...

Responding to Anonymous' Thu, Jul 8, 10:49am comments: Starting-current magnitude is determined by motor parameters. System inertia and net accelerating torque (that developed by motor less that required by load) determines the starting-current duration! An earlier reply, Mon, Jun 14...

Fred, thanks for the heads up. Regarding the wattage calcs, both approaches are valid, resulting in a multiplier of 3.24. You used the I^2R approach to calculate the coil wattages for each of two operating conditions. I used the current-square law. However, you correctly pointed out my...

Responding to Sonoman's query and Matthew Hyatt's reply: It is possible to substitute a 24-Vdc coil for a 110-Vac one in an emergency, and if the period of energization is short. I've done it a few times, but only when the substitution resulted in a current draw less than rated. However...

Responding to Matthew Hyatt's Wed, Jun 2, reply: Although you haven't seen one there is a rather simple formula for calculating a suitable shaft diameter for a given HP. If you are unable to access the reference text I noted earlier please contact me. Regards, Phil Corso, PE {Boca...

Responding to Ashok's query: Starting-current (also called inrush) is the current drawn by a motor during its runup, or acceleration, to normal operating speed. Its value is in Amperes. Typically it can be from 4 to 8 times the rated current. Ignoring the transients of the first 2 or 3...

Responding to jaibadri's query... to start: 1) Supply voltage may be unbalanced? 2) Primary taps may be improperly set? 3) What are secondary-to-neutral voltages? Regards, Phil Corso, PE {Boca Raton, FL, USA} [[email protected]] ([email protected]) {[email protected]}