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RCook... typically, the Reverse Power Relay (ANSI/IEEE Device #32) is back-up for those parameters that detect imminent failure of energy-input to the prime-mover. Some are mentioned in my 26-May-10 post. Failure of the CB to trip is a handled differently! Regards, Phil

Trilon... What is purpose of propane? Regards, Phil Corso

Karan... if you were in the USA, you would need to comply with NEC Article 110-III. However, if the equipment is associated with supply or service components then you are required to refer to ANSI/III C2, National Electrical Safety Code! Phil Corso

Raj... I have taken the liberty of interpreting your query to mean, "Is the 'time-delay' feature needed in addition to the 'reverse-power' feature?" My answer is Yes! Some Protective System practitioners have been known to eliminate the 'time-delay' because the effects and consequences of...

Hussain... typically, that information comes from the manufacturer. Phil Corso

Hussain... yours is an interesting question? The theoretical answer is, yes, losses are different. Why? 1) Neglect the effects of waveform, harmonics, and certain construction asymmetry (e.g., coil distance from the core.) 2) Input equals output plus losses. 3) Assume total...

Ralf... further to my 28-May (22:13) reply: 20) I interpreted your 27-May (13:01) comment to mean the present motor was originally operated at 480V operation, but was reworked for 208/230V? 21) Only a reciprocating-piston type compressor can be operated in either operation! The fact you...

Ralf... if further testing indicates amperes are less unbalanced, then problem could have come from improper termination of 'T' Leads! Search Control.com Archives for the following thread: http://control.com/thread/938749565 It covered Faulty Motor Terminations! Phil

James... use a "Make-Before-Break" contact arrangement on the L/R switch. Regards, Phil Corso

Ralf... 15) That messenger (is it bare?) is the ground'ED' conductor. It is carrying the unbalanced neutral-currents associated with 120V loads. 16) It probably is connected to the neutral-bar in your panel and then to the driven ground-rod. 17) My point was to determine if the A/C unit...

Jim... contact me off-line. Phil Corso (cepscon [at] aol [dot] com)

RCook... I agree with CSA. Development of the Tripping Logic Scheme is usually a collaborative effort by the facility owner's rep, the facility design engineer, and equipment manufacturers. However, in those plants I was involved with reverse-power was interlocked wth tripping parameters that...

Ralf... 9) Unless you exchanged the "T" leads an even number of times the motor could now be oerating in reverse. 10) Have you noticed a change in cooling ability? 11) Can you provide me with the amperage values that resulted in an AUF of 10%. 12) What are the Namplate Hp, Amps...

Ralf... further to my earlier reply: 8) With motor in operation, measure current in the Ground'ING' conductor that connects the supply transformer’s mid-point connection to ground (earth). Phil Corso (cepsicon [at] aol [dot] com)

Ralf... 1) While I disagree with the Ampere-Unbalance-Factor you calculated (I got about 21% with the Ampere values listed) I do agree with your conclusions. 2) Hermetically-sealed motors are often wired for dual-voltages. Perhaps, one of the phase-groups could have a reversed coil...

Walt, what happened to this idea? Phil

It's akin to putting the fox in the henhouse to protect the chickens! I can produce a number of horror stories that are available upon request. Regards, Phil Corso.

G.Rajesh... I suggest you read Thread No.: http://control.com/thread/1246285612 Regards, Phil Corso

Responding to Panthripu's 13-May-10 (06:44) query... have you searched the Control.Com archives for 'EAF' or 'Electric Arc Furnace'? Look for the thread covering Megger readings, and especially the one covering insulator tests! If you still don't understand, then provide detail...