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  1. freetown

    induced voltage synchronous motor

    The motor is somewhat old (from the 80s), and the manufacturer has limited information on it due to the departure of several staff members. What method do you recommend as the best for measuring voltage at the motor terminals during start-up?
  2. freetown

    induced voltage synchronous motor

    The amplitude of the voltage on the stator winding before the bypass contactor closes. Which manufacturer is asking: The motor guy
  3. freetown

    induced voltage synchronous motor

    Hi all, A synchronous motor 11 kV and 2.8 MW (DOL contactor) employs a series impedance (inductor) to limit the starting current during startup. After a few seconds, a bypass contactor is activated to bypass the impedance. The DC excitation is applied following the bypass. A manufacturer asks...
  4. freetown

    Factory acceptance test 11kV motor

    Hi all, We are scheduled to perform a factory acceptance test at a manufacturer for a new slip-ring induction 11kV (3000Kw, 180A, 990 rpm) motor. I am particularly interested in gaining more insight into the following tests: Withstand voltage tests: According to the IEC standard, the test...
  5. freetown

    Current clamp meter high voltage

    Absolutely not! That's why I asked if anyone has experience using a high-voltage clamp meter and what precautions should be taken. You'll find details in this link https://www.multimic.com/assets/e/instruction_manual/e-ma-HCL-5000kn+.pdf
  6. freetown

    Current clamp meter high voltage

    1. According to the specifications, Inside diameter of CT φ40mm Safe AC current measurements for high voltage circuit (up to 7000V)
  7. freetown

    Current clamp meter high voltage

    Hi all, Has anyone used a current clamp meter for high voltages (6 kV or higher)? I came across some models online claiming to support up to 7000 V, but I'm not sure if they can truly measure current in high-voltage cables.
  8. freetown

    Using of 67N and 51N

    The configuration we have is 2 incomers 1 & 2 (powered from the power plant) so two busbars with the ability to couple the two with a bus coupler breaker Some outgoing feeders are connected on each incomer busbar. We had 51N protection on each incomer but the power plant asked to disable it and...
  9. freetown

    Using of 67N and 51N

    Hi all, When we have to use residual earth protection 51N and 67N and what's the difference? Is it true that 67N is only used on the incomers and 51N on the outgoing feeders?
  10. freetown

    Uncoupled slip-ring induction motor speed

    Hi all, A slip-ring induction motor of 2700kW and 165A (stator) 990rpm, 1340V and 1250A (rotor). When we start the motor with no mechanical load (uncoupled motor so motor turns alone) we have 40A current and it's normal but what about the speed in this case, should we have a lower speed when...
  11. freetown

    synchronous motor started components

    @Gr8blu Thank you for taking time to give all these explanations. Is having an under or over excitation has an impact on how power factor is improved by synchronous motor?
  12. freetown

    synchronous motor started components

    I understand inductor in my case is used to limit (can we say reduce or limit?) inrush current for few seconds and also acting as an input filter? Today for synchronous motor, is there limiter other than inductor using in industry? For the rest of my questions i didn't really understand the answer.
  13. freetown

    synchronous motor started components

    Hi all, I'd like to know few things on how large synchronous motor works. I saw one 11kV 2.8MW with components such : Power source (from MV contactor), large inductor (for starting) and motor excitation system - From what i understand the large inductor is used as current filter, can anybody...
  14. freetown

    Regadring thermocouple sensor and calibration

    Thanks everyone for the replies, much appreciated.
  15. freetown

    Wound rotor/squirrel cage with VFD

    Hi all, I have 2 wound rotor motors each of 22 kW. We shorted the rotors at the slip ring so that it would behave like a squirrel cage one then used VFD for each. It worked well. It is now one year since and so far no problems have been recorded. My question is if i can replace the 22 kW wound...
  16. freetown

    Regadring thermocouple sensor and calibration

    Hi all, I have few questions, would like to understand about thermocouple sensors working: 1- We have some thermoucouple sensors (type T), the distance between sensors and transmitters is about 200m. As the thermoucouple output is few millivolts, is this distance can causes drop voltage and...
  17. freetown

    Looking for Mini breaker with aux contacts

    Thank you all I think i found the right one from Siemens, miniature circuit breaker 1-pole with auxiliary switch NO contact 230 V AC, 60 V DC Mini: miniature
  18. freetown

    Looking for Mini breaker with aux contacts

    Hi all, I'm looking for Mini CIRCUIT BREAKER 1 POLE 2A with aux contacts (1NO and 1NC for example) I searched but i can't find one with aux contacts, can you suggest some models?
  19. freetown

    IR Test Liquid Resistance Starter

    We had rotor winding earth faults before during starting and stator overcurrent protection reacted but the rotor is damaged or has a low insulation resistance in some cases after that. The only thing, that we don't have data on the rotor to analyse what happened because no measurement (specially...
  20. freetown

    IR Test Liquid Resistance Starter

    We use 2 or 3 cables for each rotor phase. Failure modes could be low insulation resistance of cables or the rotor itself. We have vibration probes on motor bearings.

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