What kind of motor needs star delta start?

What kind of motor needs star delta start?

2 / according to the national regulation, 7KW is about to be started with reduced voltage. In order to reduce the impact on the power grid during start-up, this problem is considered from two aspects: one is the power management department, which has an impact on the power grid when relatively large equipment is started; the other is for the consideration of users themselves, if the voltage drop is large during start-up, It may cause other equipment in the scope of the unit can not work normally. As for the size of the motor, it should consider the step-down starting, in addition to referring to some regulations, the main thing depends on the power conditions. The two units I worked in have a great difference. One is 55kW centrifugal pump, which has been started directly. Sometimes when 55kW centrifugal pump is broken, it is replaced by 95kw pump, or it is started directly, It's not a problem all the time. Although it seems that it can't work logically, it's not a problem since I've been in touch with it for 20 years. Another unit can't work. A 30kW submersible pump must be started by lowering the pressure. So specific problems should be considered in detail, The three-phase asynchronous motor must adopt step-down starting. The winding connected to triangle operation generally adopts star delta starting. The regulation is 11kw! But it also depends on the situation. You have a 75kW motor under a 500KVA transformer. You need to use it temporarily, It should not be lower than 85% of the rated voltage. 2. When the distribution bus is not connected with lighting or other load sensitive to voltage fluctuation, and the motor is not frequently started, it should not be lower than 80% of the rated voltage. 3. When the distribution bus is not connected with other electrical equipment, it can be determined according to the conditions that ensure the starting torque of the motor. For low-voltage motors, the starting torque of the motor should be controlled according to the conditions, The voltage of the contactor coil shall not be lower than the release voltage. The selection of starting mode of cage motor and synchronous motor shall meet the following requirements: A. when the following conditions are met, the motor shall be started with full voltage; when the motor is started, the voltage of the distribution bus shall meet the provisions of article 2.3.2 of this specification; mechanical energy shall bear the impact torque when the motor is started with full voltage; and; \The manufacturer has no special regulations on the starting mode of the motor. When the condition of full voltage starting is not met, the motor should be started by reducing the voltage, or other suitable starting mode should be selected. C. when speed regulation is required, the starting mode of the motor should match with the speed regulation mode