Which of the statements below are true The maximum torque of

Which of the statements below are true? The maximum torque of the motor is identical for both circuit types In star configuration the phase current is lower A delta connection offers the better speed/torque ratio as compared to a star circuit The starting current is generally lower for the star connection than delta The star/delta switch has practically no significance at all The star/delta switch permits the motor to start \"more smoothly\" In practice asynchronous motors are operated only in star configuration Draw the inner circuit of asynchronous motor according to the wye(Y) connection and also delta(A) connection. Explain why wye(Y) connection starting current is lower than delta(delta) with mathematical equations assuming that any phase\'s impedance is \"Z\".

Solution

following statement are TRUE

in star configuration the phase current is lower

a delta connection offer the better Speed/Torque ratio as compared to the star circuit

the star/delta switch permits the motor to start smoothly.

1)If Star connection has sufficient torque to run up to 75% or %80 of full load speed, then the motor can be connected in Delta mode.

2)In star connection motor is taking low current and produce high torque

3) yes, The speeds of Star connected motors are slow as they receive 1/3 voltage.

4)star connection is required at the starting o motor because a motors takes 5-10 times more current at starting5)

6)a star-delta switch permits the machine to be star-connected during the periods, with reduction of magnetiz­ing current and increase in efficiency.

7)No, Due to their simplicity, robustness and cost-effectiveness, squirrel cage motors are the preferred choice of industry. During start-up, they develop currents of up to approximately 8 times the rated current and the high starting torque linked to this.