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Hi all, Just a quick simple question. I had a problem with an elevator and the contactor was returned to me. It looks like one of the poles is slightly damanged so it looks like the motor was probably single phasing, causing burn out. My question is can a motor even drive any load with only 2...

Hi all, We had a failure of an AC to DC converting generator on the AC side. The failure coincided with a power outage. Would someone help give reasons as to how a power surge could have caused failure of the generator? Thank you in advance for any response!

Hi all, I have a question about motor wire sizing. NEC says we gotta follow table 310-16 if we will have motor wire in a raceway. However, it looks like our motor supplier provides leads that are smaller than NEC code would require in a raceway. It looks like they provided leads following table...

Hi all, I was wondering if anyone could enlighten on the following. Why do some building power supplies have more voltage drop during motor starting than others? Lets say one 50HP motor causes momentary 5% voltage drop due to transient current surge during y-d transfer. Then lets say in another...

Hi all, Would anyone chime in on what they think is the best measuring equipment for motor and motor circuit analysis? I've seen some engineers at our sister factory with portable oscilloscopes that cost close to 10,000 dollars, but I think that's overkill for motors. Would a 300Mhz. bandwidth...

Hi all, I saw the subject on contactors come up again. http://rapidshare.de/files/1496465/hb.pdf.html Please download the above. Page 3 of attachment (hb.pdf) shows wye delta starting of a 40HP/200V motor using 208V/60Hz/3Phase power supply. Scale is 250A / div. (A) and 50ms/div (horizontal)...

For a typical AC-3 Application, a certain sized starter, or more specifically, the contacts of the starter are tested to be good for 1,000,000 electrical operations under its rated application. And tests are done at a high frequency, almost 20-30 make/breaks per minute. However, for elevator...

Hi all, I'm trying to fill out a table for 3 phase ac induction motors. A 50HP motor has ratings of 148 full load amps and 808 locked rotor current at 200 volts. If power supply is 208 volts, I use a proportional equation which results in a higher locked rotor current (about 840)due to...

Hi all, For a 50HP 200V 3 phase wye-delta ac induction motor with class F insulation and FLA 148Amps and 1.0 service factor and 80 starts/hour rating (elevator duty): Is it possible to calculate insulation life/winding life/damage if motor is run occasionally above rated load for current of up...

Hi all, It is common motor knowledge that motor torque declines by the square of the change in supply voltage. However, there are motors designed for 230 or 460 volts, and torque is the same at all rpm for 230 or 460Volts, with only a change in drawn motor current. so in this case supply...

Hi all, Thanks for the help. I am dealing with a submersible system of an electric motor driving a rotary screw pump which in turn drives a piston(plunger) which raises a hydraulic elevator system. Pump Data says that for pump to operate at 3400 RPM, the minimum flow rate must be 185.2GPM at...

Hi all, for 3 phase ac inductions motors Lets say we run a motor to full speed in wye, and that line current is 120A at motor full speed RPM. Now lets say we switch to delta. Is line current for delta still 120A, and delta phase current 120/sqrt3 = 69A? Basically, at full speed rotor rpm, do...

Hi all, I'm new and have some basic questions which I would appreciate if some people could answer. How would I be able to tell a centrifugal, reciprocating, or rotary pump from each other? Also, what are basic differences and applications of each? Thank you!

Hi all, I am new to this forum and basically new to my job trying to learn about hydraulic elevator systems. We use submersible pumps with submersible motors to drive a piston which does the actual lifting of the elevator. My question is how motors are sized for pumps. From gross weight and...

Hi all, If anyone's not tired of this one yet, here is my final question on the matter. Question: Does anybody know what effects the force at which a contactor will make or break? Why would it close with so much force that it would bounce in one case causing heavy arc damage and close softly...

Hi all, It is easy for me to understand transient current surges and how I could measure them in an OPEN TRANSITION WYE start - DELTA run motor application, but all I have is a clamp on ammeter which will not catch or display the transients. What I do have is a voltmeter which can print a curve...

Hi all, I have a question and hope that someone can help. What or who determines the power supply of a building? I work for an elevator company and I see 480V about 70% of the time but then I see that sometimes there are 208V and more rarely I see 240V. For motors using wye-delta starting its...

First off, I'd like to thank all responders, some more than others... you know who you are!!! I have a problem with my delta contacts (open transition) which seem to be burning out on our hydraulic elevator systems. The only reason I heard that makes sense is because of the surge which can...

Hi all, I am trying to get an understanding of what goes on in a motor as load is increased. Say we have an elevator; with the weight of the cab alone, it will draw 200 starting amps and run at 120 amps at the lines. As load is increasingly applied, the motor speed will increasingly fall from...

Hi all, How can I make it so that someone cannot select the values in a combo box listing using VB. I want my combo box to list the values that have been entered before which cannot be used again. Thanks!!