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Jack… the Drawing you submitted is a generalized illustration of a 3-ph, 4-wire, LV (< 1,000V) distribution system. Setting aside fault-duty concerns, both sources (Left & Right) are paralleled and each Xfmr’s secondary mid-point is normally Solidly-Grounded. Unfortunately you haven’t shown...

Shaheed... to start: 1) 'Expert' is correct about using Xd" for calculating CB's Interrupting-Duty! 2) What is 16MW Generator's MVA rating? 3) What is 16MW Generator's PF rating? 3) What is 16MW Generator's Xd"? 4) Define Ur and U! 5) Was Wapda Utility's SC-duty, 31.5kA, given...

Ahmed Shahat… there are essentially two-types of Grid-Tied systems; Utility-Size, and Residential-Size! If the latter and you are in the US, the last piece of equipment on the home-owner’s property is the AC-disconnect switch located near the Utility Service panel. It must visible to, and...

Arjun Sharma... as a rule of thumb, if the Generator is a least twice the capacity of the motor, a soft-starter should work! The principle constraints are: a) The actual acceleration torque (related to kW) during run-up is usually much less than the prime-mover is capable of handling...

Sensorless... further to my earlier post, search Control.Com Achives for Power-Factor, Power-Factor Correction, or PFC! Start with thread: http://www.control.com/thread/1026187617 Regards, Phil ([email protected])

Sensorless… your statement that kVAr is “negligible” is in error. The figures you cite yield kW and kVAr values of 18.75 and 16.5, respectively! To calculate the PF correction required the utility’s PF penalty value must be known! Regards, Phil Corso

Don... thanks for the SLD. The three line-current CTs are wye-connected, and the 51N is responding to line-current unbalance. To confirm my hypothesis use the Ammeter and Voltmeter switches to read the three Phase-to-Phase Voltages, the three Phase-to-Neutral Voltages, the three Line-Amperes...

Donnapa14... mine is Cepsicon [@] aol [.] com Phil

Engineer... although their "thermal" rating may be equal, i.e., Trms = Tdc, their "Make" and "Break" constants are entirely different. Regards, Phil Corso

Engineer... Power Factor Correction (PFC) equipment location, in descending order of effectiveness, should be: 1) At the motor-side of its Starter! 2) At the motor-end of its feeder! 3) At the bus supplying a group of motors! CAVEAT: Each location must be evaluated with regard to...

Duke... this subject is quite popular on this forum. I suggest you search Control.Com Archives for "Cable Size". Start with: http://www.control.com/Thread/1026178348 Regards, Phil Corso

Donnapa14... since your setup now consists of paralleled generators the situation becomes more complex! Can you furnish a simple Single-Line-Diagram showing the protective relaying of both generators? Even a hand-drawn sketch will do! Phil

Donnapa14... typically, a 4160V, 3-ph, 3-wire, system does not have a Neutral conductor. Thus, the neutral-current you cited is derived from a residual connection of the three-line current CTs. The 75A magnitude is indicative of a severe unbalance in the 3-line currents, i.e, usually a level...

Rathore... you can find several threads on this topic in Control.Com Archives. But, the one that I think best addresses your question regarding "Steam as a coolant" is JFB's reply in Control.Com thread: http://www.control.com/thread/1387628531 Regards, Phil Corso

Donnapa14... when you say neutral overcurrent are you referring to the connection from neutral-to-ground (earth?) 1) What are line-currents? 2) What are phase-to-phase voltages? 3) What are phase-to-neutral voltages? 4) What is type of load? Regards, Phil Corso

WhoKnows... how about some data: 1) Generator nameplate data? 2) Cap size and type? 3) Has some time elapsed between the "cap" incident and not being able to start compressor? If so, have you tried rotating compressor shaft manually? Regards, Phil Corso

Muni... to give you my idea of a Fast-Valve app, following is one approach you might want to consider: The App was a Paint-Pigment Dispensing Machine! The fluid-volume to be dispensed amounted to 0.3 cubic-centimeters for each operation of the valve. A standard Solenoid-operated valve...

Muni... my earlier post neglected to ask you to define "On-Time" duration? Phil Corso

Muni... if it's an electrical solenoid the desired On-tme" of 0.2 second (armature-travel) can be easily achieved by altering the applied voltage. Regards, Phil Corso

Arjun... can you provide additional data: 1) Was the UV-relay measuring the 11kV, 33kV, or 6.6kV voltage? 2) What is size and %impedance of the 11/33kV Xfmr? 3) What is size and % impedance of 6.6kV Captive-xfmr between 33kV Xfmr and Mtr? 4) What is size and distance of 11kV line...