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  • Users: GGOSS
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  1. GGOSS

    2 x 1.5MW 11kV Slip ring Motors with liquid resistor starters

    It appears the original question has not been answered. If the motors are directly coupled, they will balance themselves and therefore there is no need for tuning/load sharing resistors. If the motors are indirectly coupled, it becomes necessary to analyse and address both the ‘start’ and ‘run’...
  2. GGOSS

    EMC issues with VFDs

    Great work Mark.
  3. GGOSS

    Lifting and holding capacity?

    Unfortunately no data sheet for the motor asimpson. Can we assume a value for the sake of the exersize. Then maybe I can repeat the calcs once the motor torque details are known.
  4. GGOSS

    Lifting and holding capacity?

    Thank you desertfox, I am actually comparing a couple of winches and have found the manufacturers published data on max lift and max hold to be very different even though the products appear very similar eg same motor and gearbox. Also, as neither are prepared to give me a straight answer, I...
  5. GGOSS

    Lifting and holding capacity?

    Hi guys, I'm electrical, not mechanical so please excuse me if my question seems a little basic :) I am looking for advice/guidance on how to calculate maximum lifting and maximum holding capacities (preferably in kg) for a drum style winch with the following details. Drum diameter - 250mm...
  6. GGOSS

    PCS Soft Starter

    The choice of starting mode really depends on what you want to achieve out of the product. It is true that both will provide reductions in starting current and minimise, but each performs these functions differently. Soft start will allow the motor to develop and increasing amount of torque as...
  7. GGOSS

    PCS Soft Starter

    From personal experience the current does not need to fall below 50% of the min FLC setting for nuisance phase loss/open load trips to occur. We know that it can and does occur when the run current is less than 50% of the max FLC setting and suspect this is influenced by current imbalance and...
  8. GGOSS

    Soft Start - Starting Current for Centrifugal Pumps

    A current limit/start current setting of 300 - 350% motor FLC would normally enable the motor to develop enough torque to accelerate the pump to rated speed. Most soft starters these days will operate correctly within a specified frequency range. Once outside this, the starter will trip in...
  9. GGOSS

    Danfoss softstarter MCD500

    If the hydraulic conditions are identical every time a soft stop is called, I would expect flow and presssure to be fairly consistent also..........but I'm no hydraulic expert that's for sure.
  10. GGOSS

    480 ac motor with soft start fails at startup

    Do the breakers have a thermal magnetic release or just a magnetics release? Sounds to me like they may havea thermal release also, but I'm unsure from the information you posted! What type of machines are the motors driving? Is it possible the breakers are tripping on thermals due to the...
  11. GGOSS

    Danfoss softstarter MCD500

    Hahahahaha. Yes, something like that. :). How are you going jraef. It's been a long time!
  12. GGOSS

    Danfoss softstarter MCD500

    Sorry for the late response, I don't get on here as often as i use to. AAC learns the characteristics of the motor and load through feedback received during the first few start and stop cycles. Each subsequent start and stop brings the acceleration and deceleration of the motor and load closer...
  13. GGOSS

    Danfoss softstarter MCD500

    I have direct experience with the product from which the MCD500 was derived. AAC is suitable for applications that are consistent in their behaviour. That is to say it is a function that learns the application, and if the application is changing it cannot learn.
  14. GGOSS

    Slip Ring Motor operating like Squirrell cage Motor

    Yes, it should read torque electricpete.
  15. GGOSS

    Sizing bypass contacts for Soft Start

    The use of a line/isolation contactor also acts to increase stsarter reliability particulartly in areas where power quality is questionable. SCR's are most vulnerable to damage from voltage transients when they are connected to supply but NOT gated on. The addition of a line contactor...
  16. GGOSS

    Volt Drop Calculation with Auto transformer

    The current drawn form the supply will be 0.7 x 0.7 x LRC plus a little extra to cover the losses. The current delivered to the motor will be 0.7 x LRC. The current drawn from the supply is what you need to woprk with.
  17. GGOSS

    Locked rotor definition

    This may appear a little harsh but it is the esponsibility of the commissioning engineer to ensure the motor protection relay is programmed correctly. If the thermal withstand curves for the motor are not available or if the motor protection relay cannot be programmed to protect the motor...
  18. GGOSS

    Circuit Breaker sizing for VFD and soft starter circuit?

    In fact "sizing a circuit breaker of a soft start circuit in the same way as in full voltage starting" is recommended. Although starting current is reduced it is drawn for a longer period of time. The theoretical I squared t is the same in both cases. Some people will select a smaller breaker...
  19. GGOSS

    3 phase Motorboss soft start

    To the best of my knowledge it is not possible. With regards to motor overload protection and AB, I can confirm they introduced it with their SMC Dialogue products and have continued to offer the functionality in the SMC 3, SMC Delta & SMC Flex. The AB STC, SMC2 and SMC Plus products did not...
  20. GGOSS

    3 phase Motorboss soft start

    As a soft starter, the Motorboss product offers very basic open loop controlled voltage soft starting. I suspect you would get a much higher level of soft start functionality, and a better buy price by going to one of the majors.

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