Single Phase Induction motor winding phase difference

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SUMMARY

This discussion focuses on extracting electrical properties of a single-phase induction motor, specifically measuring the phase difference between start and run windings. Participants discuss using torque vs. slip curves and the equation Torque*c1 = c2*s/(1+(j*w*t)) to determine the rotor's time constant (L/R). Additionally, they explore calculating capacitor values for achieving a 90-degree phase shift using phasor diagrams, emphasizing the relationship between capacitive reactance, capacitance, and frequency.

PREREQUISITES
  • Understanding of single-phase induction motor operation
  • Familiarity with phasor diagrams and electrical circuit analysis
  • Knowledge of torque vs. slip characteristics in motors
  • Experience with curve fitting techniques in electrical engineering
NEXT STEPS
  • Study the method for measuring phase difference in motor windings
  • Research curve fitting techniques for electrical models
  • Learn how to construct and analyze phasor diagrams
  • Investigate the calculation of capacitive reactance using capacitance and frequency
USEFUL FOR

Electrical engineers, motor control specialists, and students studying motor dynamics and electrical circuit analysis will benefit from this discussion.

Vikas Kasireddy
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Q1:
So I'm trying to extract the electrical properties of a single phase induction motor. First off, how am I supposed to measure the phase difference between the start and run windings? I have L and R of start and run windings too!
Q2:
I have a torque vs slip curve up until 130% of rated load. Using this I was told I'm supposed to curve fit this data to the equation Torque*c1 = c2*s/(1+(j*w*t)) to get the time constant t of the rotor (or L/R of the rotor). I'm not sure how I'm supposed to do this. I also have this L/R value using the electrical model that I found with locked rotor measurements.
Q3:
If this system was to be switched with a capacitor to get 90 degrees phase shift, how do I calculate the capacitor value? I know I'm supposed to draw a phasor diagram and find the value of C so that it forms the required phase shift but I need more explication on that.
 
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For the phasor diagram. You should have a phasor pointing somewhere in quadrant I (up and to the right). Up is for the inductive portion, and horizontal is resistive portion. If you create a right triangle from this coming back down to the Real axis, this vertical leg coming down will be your capacitive phasor.

Do you know how to calculate capacitive reactance from Capacitance and Frequency?
 

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