electricpete
Electrical
- May 4, 2001
- 16,774
I am pondering the meaning of stator winding pitch and distribution factors and what they tell us about motors.
Here is one thing I believe. If we have a motor with the stator energized by 3-phase sinusoidal 60hz, and rotor locked to prevent movement. If we neglected saturation (perhaps energize the motor at lower voltage in physical experiment), I believe there will be no current harmonics. Does anyone agree or disagree.
Here is my reasoning:
We now have a pure linear system. The phase voltages are the inputs (independent variables). The outputs (dependent variables) are fluxes and currents... these are all determined by linear operations (addition, scalar multiplication, differentian integration), and the system itself is not time varying (even though state variables are time varying of course). For a linear system excited by single-frequency sources in steady state, all state variables will be at that same single frequency.
Now if we allow the rotor to move we have a time-varying system introducing non-linearity, creates rotor mmf harmonics at frequency rotor-bar-pass frequency +/- 1*LF and current at same frequencies. Likewise saturation would allow currents at odd non-triplen harmonics.
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Here is one thing I believe. If we have a motor with the stator energized by 3-phase sinusoidal 60hz, and rotor locked to prevent movement. If we neglected saturation (perhaps energize the motor at lower voltage in physical experiment), I believe there will be no current harmonics. Does anyone agree or disagree.
Here is my reasoning:
We now have a pure linear system. The phase voltages are the inputs (independent variables). The outputs (dependent variables) are fluxes and currents... these are all determined by linear operations (addition, scalar multiplication, differentian integration), and the system itself is not time varying (even though state variables are time varying of course). For a linear system excited by single-frequency sources in steady state, all state variables will be at that same single frequency.
Now if we allow the rotor to move we have a time-varying system introducing non-linearity, creates rotor mmf harmonics at frequency rotor-bar-pass frequency +/- 1*LF and current at same frequencies. Likewise saturation would allow currents at odd non-triplen harmonics.
=====================================
Eng-tips forums: The best place on the web for engineering discussions.