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Recent content by Walden

  1. Walden

    Power savings

    You appear to be an industrial user if so; you may have a kVA meter rather than a kWh meter. If you have, then you will save on your electricity bill if you improve the power factor.
  2. Walden

    Star-Delta Starter: Open or Closed Transition?

    As a matter of interest, how much are you out there paying for your closed transistion resistors? Here in the UK I have quotations from £275 to £321 for a three section resistor in a ventilated box suitable for 4 starts/hour for 2 seconds: motor current = 240A at 400V. Carriage costs extra...
  3. Walden

    Y-Delta starters in elevators

    Many years ago, I saw a star/delta starter with only two contactors. The star contactor had normally closed, fully rated contacts on the top with three normally open main contacts underneath. Is this the beast?
  4. Walden

    Tripping Circuit Breaker on Wye to Delta Transition

    This can be a real pain in the neck! I've just had an installation where two of the three 150kW motors started OK and the third identical motor kept tripping the breaker on changeover to delta (all open transition). In the end, swapped the breaker to another manufacturer and all is now OK...
  5. Walden

    Part Winding Motor, Starter Timing

    On refrigeration compressors with part wind motor windings, the time between the two windings is often 1 second: many times 0.5 second and I have seen the delay to be the time taken for the auxiliary contact on the first contactor to start the second. The killer of refrigeration compressor...
  6. Walden

    How To E-Stop A Powerflex Drive

    To emphasise what jraef wrote. As an engineer you have to decide how quickly the plant is to stop in an emergency. For example, two projects I have worked on. In the first, a cable winding machine, we used DC injection braking to stop the drum dead in half a revolution.In the second,the load...
  7. Walden

    Jobbing Electrician

    In my haste to send the original post I wrote "Jobbing" when I should have written "Journeyman".
  8. Walden

    Motor starting problem

    Are you certain that the compressor is started unloaded?
  9. Walden

    Jobbing Electrician

    From time to time, some of you describe yourselves as “Jobbing Electricians” or “Jobbing Engineers”. Does this mean that you are self-employed and move across the US from project to project? It is a job title that has not crossed the Atlantic.
  10. Walden

    Motor starting problem

    I multiply the FLC x 1.5 to find the rating of the MCCBs on these types of starters.
  11. Walden

    Sizing conductors of shielded wire for 4-20 loops?

    I like the sound of 18 AWG! Over the years I have discovered, on site, just how much time it takes to strip the insulation off small cables without breaking the strands and then trying to get a cable ferrule to fit over the strands and get a good connection into the terminal. Life is a lot...
  12. Walden

    Contactor connection question

    I have seen a star/delta starter with no main contactor at all! Three of the six motor winding terminals were permanently connected to the three phase incoming supply through fuses. A star and a delta contactor only were used to start the motor. The thermal overload relay was fitted to the delta...
  13. Walden

    Water pump Wye/Delta Starter

    I am replacing three wye/delta 30kW motor starters. The existing starters are closed transition with a small resistor bank. The client wants to take out the the resistor bank because it frequently burns out and repairs are difficult and expensive. What are the implications of fitting an open...
  14. Walden

    Motor Colour Connections

    Thank you all very much! The motor is up & running. The Hanning web site came up with the answer from Gerald Stork. This is a motor manufactured about 22 years ago! When it came to me someone had removed and lost the terminal box and all I had were the loose leads. The connections are as...
  15. Walden

    Motor Colour Connections

    Hanning
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