Developed soft starting for 3-phase induction motors

The highest value of the maximum acceleration during starting is equal to 86 rad/sec2, and that is achieved if the motor is started by a single-ramp voltage. As said before, the maximum per-unit input current equals 2.45 pu, if the motor is started by single-ramp, second-order, and sinusoidal voltage. This maximum per-unit input current equals that if the motor is started direct-an-line.14- from (7-2), the highest value of the minimum starting time is 2.73 sec, if the motor is started with second-order equation. The smallest value of the maximum acceleration during starting equals 86 rad/sec2, if the motor is started by (V/f= 3.96). The energy loss, if the motor is started by (V/f= 3.96), equals nearly, 19% of that if the motor is started direct-on line. The smallest value of the maximum per-unit input current is equal to 1.5 pu, if the motor is started by (V/f= 3.96).15- from the above two items (13 and 14), the best method of starting is that if the motor is started by (V/f= 3.96). This is because of the small values of the input currents, the energy loss and the maximum acceleration during starting.Future Work:1- A study for starting with three or more ramps voltage for loads which vary with speed.2- A study for starting with second order equation of voltage and frequency variation.3- A study for starting with sinusoidal voltage and frequency equation.4- A study for control on the applied voltage at running condition by taking a signal indicating the required load torque during running.