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Thank you for your helpful reply. I discussed this with a cable "cleat" manufacturer and they claim that the SOOJ jacket is not rated to withstand the repulsive forces generated as a result of short circuit currents. They claim the jacket will most likely fail violently above 18 kA. In this...

thread238-191953 I'm trying to find some information about Cable Deflection during short circuit conditions on a 3 phase four conductor "drop" cables. I remember seeing a video about cable deflection during a short circuit and seem to remember the unsecured cables move about violently. Is...

The DC supply is basically a 480 VAC VFD operating in the regenerative mode. The problem is the AC Grid-Tie inverters (Load) are rated only to 570 VDC max. Splitting the DC bus would allow safe operation within the device ratings as long as one-half of the DC bus does not short. The only...

The two loads rated 350 VDC have their own DC Bus capacitors, and loading is fairly symetrical. Test show that the DC 1/2 Bus voltages quickly drift & one half assumes more load than the other (voltage imbalance).

I am looking suggestions on how to achieve balanced loading of a 700 VDC bus without incurring large power losses using bleed resistors. The buss consists of two 450 VDC rated capacitor banks conected in series. The loads are to be connected across each capacitor half-section. The loads are...

My apologies, the voltage transducer is a Flexcore VTU-012X5, I did not see a CMMR value listed. The Positive 7 vdc pulse is lasting approximately .4 mS with 4.47 vdc being the trip setpoint. RC filtering at the controller signal input has not improved the situation...

Currently the inverter has not been subjected to loads other than magnetizing & windage for a 10 HP 4 pole motor. The initial inrush has not been measured yet. I will look into increasing the gate drive resistor value to provide softer switching. Thank you for the feedback. Best regards...

Yes, the DC Bus capacitors are of the Low ESR electrolytic type. There are 2.0 uF film caps across C-E at each IGBT half bridge, and also across the input rectifier. The design requires 6800 uF total bus capacitance, switching to film type (pulse) capacitors would require considerable space...

The suggestion of using the LEM Voltage transducer was implemented. Now we are experiencing inverter trips on DC bus overvoltage faults. RC filters have not remedied the noise issue due to switching of the IGBTs. Nominal DC bus voltage is 670 Volts, V-Transducer output 3.5 Vdc @ 670 Vin...

What methods are employed for measuring a 680 VDC bus to provide a 0-4 VDC feedback signal to a microcontroller ADC. The DC bus consists of 2- 450 VDC capacitors connected in series. I had initially considered a voltage divider measuring from the capacitor center tap to positive, but this would...

Sorry, The question was answered while I posted my last reply. Thanks to all for the help! Bosko

OK, going back to my initial question on Megger testing devices under vacuum. The breaker must be evacuated to much lower level to achieve its dielectric properties. I would then assume Vacuum Insulated Circuit Breakers emit X-Rays while in their open state with rated voltage applied to the...

Excuse my ignorance, what purpose does the vacuum serve in a "vacuum circuit breaker" non CF6 charged? (other than preventing oxidation of the contacts) Whould it not ionize the gap & flash over at a lower potential? Bosko

Numerous HVAC & transformer technical manuals warn not to Megger equipment under vacuum. Why? A vacuum is close to a perfect insulator. What is the reasoning for the caution? Thanks,

Could someone please help me understand the meaning of "Mean Length of Turn",and "Effective Turns Ratio", (how these relate to Perm. Split Cap Main/Aux windings) Also, any recomended reading on AC Motor Design.

The motor is indeed a 12 lead unit. Just wanted to confirm that the coil design is specific to either delta or wye connections. Individual coils are designed to see either 133 volts or 230 volts. This is more a question of theory & not a particular application. Thanks you for the replies...

This is for a unique application in which the motor is actualy run on single phase power, with phase shifting caps. It would be a little difficult to describe in short. Getting back to the coil voltage question, is my assumption correct? Thanks, bobo480

I am trying to run a 75 HP dual voltage Delta wound motor (230/460)in a parallel Wye configuration with 460v L-L. My understanding is that the coils will see 265 volts vs 230 volts in normal delta configuration. Though the coils see a voltage which is 13% higher than rated, I would think the...