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  1. VermontPE

    Physics of motor startup

    cswilson Finally what I have been trying to get to. Thanks! Tom
  2. VermontPE

    Physics of motor startup

    A concept not yet discussed is the idea of resonance. Does changing the rotor resistance change the resonant frequency of the rotor's impedance, matching (or unmatching as the case may be) the frequency of the rotating field with the resonant frequency of the rotor?
  3. VermontPE

    Physics of motor startup

    Here are some more possible mechanisms...ignore the wound rotor and imagine different designs of bars in a squirrel cage motor. Some of the rotor bars are in regions where the effective field is very nearly zero. Increasing the resistance of the bars can force more of the total current to flow...
  4. VermontPE

    Physics of motor startup

    jraef, Every graph I look at for wound rotor induction motors shows the torque peak moving from high speed to low speed with increasing rotor resistance. If the resistance is low, the startup torque is low. If the resistance is high, the startup torque is high. What is the physics of this...
  5. VermontPE

    Physics of motor startup

    I am trying to come up with a satisfactory description of the physics involved with a typical full-voltage induction motor startup. Assume the motor is a typical induction motor driving a constant torque load that is full load at rated RPM. Basically, what happens with the voltage, stator...
  6. VermontPE

    High starting torque, low running power

    I agree Lionel, wye-delta is interesting but counter-intuitive to the idea of saving energy. I'm trying to get a real motor datasheet to show the efficiency running in wye vs delta.
  7. VermontPE

    High starting torque, low running power

    Thank you very much everyone for the replies. aolalde, your VFD reply seems a bit strange - we have thousands of VFDs in our company. Roughly 80% of the ~70MW worth of motors we have in NA are VFD. Of those I have never adjusted one to reduce the output voltage but maintain the same...
  8. VermontPE

    High starting torque, low running power

    I have a process driving many screw conveyors in a mining facility. The material being conveyed is a fine powder. Generally we try to empty the conveyors at the end of a production run, but sometimed residual material is left in the conveyors. When this happens we need high torque to get them...

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