240 or 415
The timer is used to give the motor time to reach its running speed at the star voltage. Once the timer times out the star contactor drops out and the delta contactor pulls in.
It is a type of starter that allows a motor to be started across the line by starting the motor with a reduced inrush current. The motor is started in a wye configuration until it gets up to speed and then a timer drops the wye contactor out a draws the delta configured contactor in. The motor then operates in a delta wired configuration.
That is the star point contactor that opens when it goes into the delta configuration.
the important is contactor, timer, olr.....
The link in the star contactor is used to form the star point of three of the motor leads. On most star wound motors the star point is inside the motor windings. On a motor that can be used for star delta starting it is a six wire motor. The star point winding depends on the contactor to tie the coil ends together externally in the control panel of the star delta starter.
The N.C. (timed open) contacts in the star delta timer energize the star contactor's coil when the system is energized. At the same instant the system is energized, the timer starts to time down the required time which lets the motor get up to speed in the star configuration. When the timer reaches the set point time, a second set of N.O. (timed closed) contacts close the delta contactor's coil and open the N.C. timed contacts of star contactor's coil. The motor now runs in the delta configuration. When the system is de energized the timer contact's reset to its de energized state.
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One of the three phase contacts in the star contactor could be burned open or just open not allowing the motor to start because of a single phase condition. The time interval between star and delta connections could be small enough that the motor heaters will not catch the single phase condition and trip. When the motor goes into delta (which is now across the line starting) all of the three phase contacts in the contactor close and the motor starts.
rotor contactor are used to cut the resistance in slip-ring motor connected through resistance box. resistance is proportional to torque. so by controlling rotor contactor resistance can be controlled and hence torque can be controlled. for more information check torque and speed characteristic of wound motor.
In motor starters, this is usually done using contactors. Explanation of this can easily be done using a circuit diagram. There are three contactors, the main, star and delta contactors-all these contactors can be the same type. There are many ways of wiring a star delta but here I will only give a generalized answer. First, the main contactor and star contactors are energised thus the motor runs in star. After about 5 seconds, the timer which gets energized at the same time as the main and star contactors, switches its CONTACTS i.e the normally open closes and the normally close opens. This dienergize the star contactor and energized the delta contactor. Thus, the motor now runs in delta.
A lot of designers will fit an under rated star contactor, partly for cost saving purposes and partly down to the fact that the star contactor will only stay energised for a brief period. Burning out the star contactor could be down to it staying in circuit too long, not changing over to delta, a timer malfunction holding in the star contactor or switch that is defective in the control circuit. Another cause could be your motor is drawing excess current.
A delta starter supplies what ever the supplied voltage to the line side of the contactor is. The inrush current is usually 300% of the full load amperage of the motor. Edit to above answer: Actually the question is for a Wye-Delta Starter (Wye=Star). There are two contactors, one in Wye configuration and one with Delta. The Wye is used to start and the Delta for run. This is a reduced voltage start scheme. Though the line supply voltage remains the same, for instance 480VAC, the phase voltage at the motor will be different for the Wye: V(phase) = V(line)/1.732 In a Delta V(phase) = V(line) So the Phase Voltage during the start will be 277VAC and then when the motor is spinning, usually after a set time delay, the Wye contactor drops out and the Delta contactor kicks in so that Phase Voltage is now the full 480VAC.