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  1. KllrWolf

    Which current is used for rating AC induction motor leads

    I agree with Jraef on the definition of motor leads. in submersible motors, the leads are the amount of wire coming from the windings, out of the motor, and what the cable is spliced to. The leads are sized based on FLA and always being submerged in the fluid. this can lead to funny splice...
  2. KllrWolf

    Overspeed with a VFD

    I second mikekilroy. As a motor manufacturer, a VFD automatically drops it to a 1.0 service factor on the motor.
  3. KllrWolf

    Starter Type

    In fluid filled submersible motors, DOL is the preferred by the motor, as it uses the speed to get the fluid wedge required for the bearings. If the motor is not spun up fast enough, you start to damage them.a rough guideline is for the motor to be up to speed in about 4 seconds (or less). Our...
  4. KllrWolf

    Overspeed with a VFD

    Rewinding a 2 pole to a 4 pole is an issue. For one, the same horsepower requires a larger frame. In the fluid filled motors I deal with, a 75 Hp 2 pole is an 8" motor and a 4 pole is a 10". Second is the torque, a 4 pole creates about double the torque at the same Hp. Depending on the...
  5. KllrWolf

    Overspeed with a VFD

    An induction motor speed is based on the frequency of the power, thus a 2 pole motor will run at 3600 RPM at no load and 60 Hz source (3000 at 50 Hz). At load the RPM actually drops as the load increases. A synchronous motor is designed to run at a specific speed that stays at that speed even...
  6. KllrWolf

    Overspeed with a VFD

    Yes, running a motor over sync speed does create more issues. Many times you could also be running into a critical frequency not too far above the sync speed, in addition to greater heat and other losses.
  7. KllrWolf

    Squirrel Cage Rotor Testing

    Thanks everyone for the information. It has filled in the blanks, and gave me good places to look up more details.
  8. KllrWolf

    Squirrel Cage Rotor Testing

    We have someone asking us about rotor testing for broken/cracked bars and joints. We use the growler test on all the rotors. They brought up an induced current loop test in the spec they sent us. I can find information on testing the stator, but the test on a rotor is slim information. About...
  9. KllrWolf

    First Turn Failure on submersible pumps

    From what I have seen, the common mode filter does not prevent failures. From discussions I have had with a few VFD manufacturers, the common mode filter as they build into the VFD does not do anything to the signal, and the same filter would be required if the VFD had a common mode filter or...
  10. KllrWolf

    Induction Motor or Generator EMC/EMI Testing?

    A DOL induction motor should not cause any distortions on the power line except for changes in power factor or voltage level, which would be constant with a constant load. If the load is capable of running the motor during operation, you might get some power generated back if it spins it over...
  11. KllrWolf

    First Turn Failure on submersible pumps

    Do not forget that each time the signal hits an impedance mismatch, there is a voltage reflection. Normally this would only occur at the motor, but with the submersible, you will get one at both the motor as well as water/air interface. This causes the potential for there to be another...
  12. KllrWolf

    My new book - any thoughts?

    The book is sounding awesome. The inline definitions with index would work well. I may not deal with automation as a job, but I do need to know those kinds of things to help our customers. I am definitely interested in getting it once you finish it.
  13. KllrWolf

    My new book - any thoughts?

    My ideas are less about the technical aspects than as a book. If it can/ment be used as a reference I would say make sure it has a good table of contents, a good index, and at least a basic definitions section. I have several different reference books that have great information, but they lack...
  14. KllrWolf

    First Turn Failure on submersible pumps

    I have heard of it being done for voltage purposes, however they still used a filter between the VFD and the transformer. I do not know how well a transformer would preform as a filter on its own or the cost of a transformer versus a filter for just filtering purposes.
  15. KllrWolf

    First Turn Failure on submersible pumps

    Unfortunately, that would not work with the motors I deal in. You would have to make the VFD be able to be full submerged in a well. On top of that is the size restriction. We have 300 Hp, 2 pole motors that are designed to fit into a 12" diameter well, with the 4 pole version fitting inside...
  16. KllrWolf

    First Turn Failure on submersible pumps

    The cable used is usually not considered twisted cable. It is usually called ship or marine cable by the suppliers. It is three conductors, with or without ground, encased in an outer jacket. Flat cable is also very common in wells. The air/water interface is an abrupt change, as is the...
  17. KllrWolf

    First Turn Failure on submersible pumps

    Most of the cable used is not armored or screened. If any is, we are not informed of it, unless the motor is ordered with it. I wish I had more information about any difference if armored/screened cable is used, such as if it made the problem better or worse. The problem is that nobody wants...
  18. KllrWolf

    First Turn Failure on submersible pumps

    That is correct, NEMA MG1 does not address submersible motors besides the shaft and mount face on some of the smaller sizes. It is the environment of the submersible motor that is the problem. The cable has an impedence mismatch at the water/air interface as well as at the motor. As an...
  19. KllrWolf

    Motor Failure

    I would agree with the turn to turn fault. The pictures of the stator do not show any signs of rotor contacting the stator enough to overload a winding. With rotor to stator contact that great, you would expect to see deformation in the teeth, if not parts of the teeth broken off. The...
  20. KllrWolf

    Future of Electric Motors

    The latest and greatest for my tiny segment is just an increase in larger horsepower motors than previously built, and the use in either colder or hotter ambient conditions than normal.

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