星三角（Star triangle）.doc

星三角（Star triangle） Typical application control line analysis In the conventional Y- Delta motor control circuit, a time delay relay control of the motor in Y form effective control switch to start a shape to run. Press the start button control circuit of Y- Delta SB2, time relay KT electric power at the same time, the KT instantaneous contact self-locking for SB2, KM3 electric contactor coil, KM3 main contact is closed, the normally open auxiliary contact is closed, the main circuit of KM1 contactor is electrified, the main loop is switched on; KM3 normally closed auxiliary contact disconnect, ensure the contactor KM3 work, KM2 can not work, the motor is in the starting state Y. When the time delay relay KT arrival (KT time can be set according to the power control of Y- delta starter motor set). Time delay relay normally open and normally closed contact switching delay, resulting in KM3 AC contactor coil power, the main contact is disconnected, the AC contactor KM2 power, the auxiliary contact self-locking on KM1, KT contact, ensure the AC contactor KM2 operates, the motor running in the form. Time relay electromagnetic compatibility Application environment of time relay As an automatic controller, time relay is widely used, especially when it is used in low voltage electrical equipment control network, there are many electrical equipment environment, the electromagnetic interference problem is more serious. Damage the internal components of the composition of the time relay was not caused by time relay fault (failure) of the main reason, but in a variety of applications in interference directly into the time relay through electromagnetic coupling, capacitive coupling, disturb the normal time delay control. Whether the time relay can work normally in this interference environment will affect the normal logic function of the whole automatic control system, and even may cause great quality accidents and economic losses. So the time relay in a variety of harsh environ