With a contactor we can control the power connection to the motor (power on/off). A typical AC contactor comes with 4 terminals aside (L1,L2,L3,A).
'A' has A1,A2 terminals which are of the magnetizing coil. By magnetizing & demagnetizing A1-A2 coil, power line connections to motor can either be made or broken. This is a simple DOL (Direct On Line) application.
Further, reverse/forward circuits and star-delta circuits can be constructed based on the requirement.
A contactor's role in whatever application is 'making or breaking' the contact.
The coil supply can either be AC or DC.
Look at the amount of current that the contactor plate can handle. The motor current must be lower than the current that the contactor can handle.
As well as motors, contactors also have kW and Ampere ratings. Have a look on the name plate of your motor and you will see its maximum current draw (amps). Select a contactor with a current rating greater than this.
A definite purpose contactor is designed (and rated) for a specific load. So a lighting contactor is one example of a definite purpose contactor. A motor starter contactor is another example. So, a lighting contactor is a definite purpose contactor, but a definite purpose contactor is not necessarily a lighting contactor (it might be a motor starter, for instance).
See discuss question below.
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.
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.
Motor started will have overloads the contactor connect es line voltage.
explain me about the contactor works with examples. if i want to control a motor with contactor. and how i can use contactor in loops with over load and circuit breakers.
As well as motors, contactors also have kW and Ampere ratings. Have a look on the name plate of your motor and you will see its maximum current draw (amps). Select a contactor with a current rating greater than this.
One way is to use the auxiliary contacts on the motor contactor to close a separate source supply to drive an auxiliary relay.
On the load side of the contactor. T1,T2,T3.
From the bottom of the motor contactor's heater block you connect the motor's leads to T1, T2 and T3. If the motor rotates in the wrong direction reverse any two leads on the bottom of the motor's contactor heater block.
A definite purpose contactor is designed (and rated) for a specific load. So a lighting contactor is one example of a definite purpose contactor. A motor starter contactor is another example. So, a lighting contactor is a definite purpose contactor, but a definite purpose contactor is not necessarily a lighting contactor (it might be a motor starter, for instance).
contactor
See discuss question below.
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.
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.
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.