Recent content by luis7006

Hello, I thank your answers! Just one additional question: We modeled a load using a square torque approximation and the motor starts faster with this load that without it. Could anybody give us a clue or tell us why? Best Regards

Hello, We are currently simulating the motor starting of some large medium voltage motors. I have some questions that I hope to receive your feedback to understand: 1) Manufacturers' catalogue state intertia. Is this value the inertia value for the motor without load, I mean, only the rotor...

Hello, I thank your responses, they are very usefull! However, the main question is: Why does not IEC Std for shorcircuit calculations determine thermal and breaking currents for two phase faults? What I have seen is that the three phase fault is the highest current magnitude unless, there...

Hello, I thank your answer, however our concern it is not related to the magnitude of the values. It is oriented mainly to the customer requirement to "see" all of the values for all of the faults.

Hello, I would like to receive your feedback related to shortcircuit analysis using IEC 60909 methodology to calculate two phase and two phase to earth faults because, there are not all of the currents determined by the software. We already read the standard and it talks about only initial and...

Hello dpc Thank for your answer! The motor is 1510 kW at 1187 rpm. As you can see it is a large one that suppossely will be started with "a rotor resistance". I will contact the manufacturer to see if there is an error or how to understand the given values. Best Regards

Hello, I would thank your advice about the following: From the technical data sheet of a slip ring motor, we have: Starting time of 25 seconds Stall time (cold/warm) 3/2 seconds We think there is an error because the stalling time should be longer than the starting one, isn't it? Any...

Hello, I am in doubt about the correct ANSI factor to determine the damage curve of a transformer. According to the well know procedure, it is said that if the transformer windings are delta-delta a factor of 0.87 has to be considered for all current values. In the same way, if delta- wye...

Hello, I would like to receive your feedback about: How can we determine the number of starts per hour or allowable conscutive startings of a motor? If we have not available information, how can we specify this?? We have read that NEMA defines a typical 2 colds/1 hot starts, this could be a...

Hello everybody, Does anybody know something about short courses for stability (the basic concepts) and also for harmonic filter design? I will thank your answers/comments Best Regards

Hello, I also recommended you before to make any change of the fuses, firstly monitoring the rms current through this circuit (trx input)and in that way be sure about the total current. You may have some high harmonics content that combined with high loading may cause low voltage and then...

Hello, Another good option is DIgSILENT www.digsilent.de You can model each device with its own harmonic characteristics

Hello friends, I would like to receive some feedback from you related to how to size the zero sequence CT for a Micom P211 relay. In this case, there are no CT's in each one of the phases and we will use an external "window CT" to sense zero sequence current and in that way providing a 51G...