Star delta starter
Circuit principle of star delta starter: Y - △ step-down starting control circuit was the most commonly used electrical circuit when electronic equipment such as frequency converter and soft starter were expensive and the technology was relatively backward. With the development of science and technology, this starting mode has gradually been eliminated, but the interlocking, self-locking Time delay relay, winding connection of motor, etc. are good teaching materials for those who just touch the circuit. Now we will introduce the working process and current voltage relationship of the star delta step-down starting circuit according to the star delta step-down starting circuit diagram. Working process of star delta starter: close QS, press St, KT and KMy are powered on. KMY-1 closes and KM is powered on; KMY-2 is closed, motor coil is in star connection, KMY-3 is disconnected, KMY and KM △ are interlocked to avoid KM △ maloperation, KM-1 is closed, and self-locking start button; KM-2 closing is ready for triangle work; When kM-3 is closed, the motor is powered on and in star start state. After the time delay of the time relay has reached, the time delay contact KT-1 is disconnected, the KMy coil is powered off, KMY-1 is disconnected, and KM is still powered on through KM-2; KMY-2 is disconnected to prepare for the triangular connection of motor coil; KMY-3 is closed, so that KM △ is powered on; KM △ - 1 is disconnected and stops supplying power to the time relay coil; KM △ - 2 is disconnected to ensure that KMY cannot be powered on for misoperation: when KM △ - 3 is closed, the motor coil is in triangle operation state. In the triangle running state of the motor, the SP stop button must be pressed to make all the contactor coils lose power and trip, and then stop running. 3. Voltage current relationship in star delta step-down starting When star starting: the voltage on each coil of the motor is 220V current I star=U star/Z triangle starting: the voltage on each coil of the motor is 380VI angle=U/angle ZI star/I angle=U star/U angle=220/380; The voltage of star start is about 1/3 of that of triangle start. Star delta start, current=0.33Iq, voltage=0.58Ue, starting torque=0.33Mq. To sum up, star delta step-down starting is a step-down starting mode at the expense of starting torque. Although the starting current is reduced, the torque is sacrificed and can only be used in general light and medium load fields.