What is the capacitor?

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 The Capacitor.         A capacitor is formed when two conductors, usually of aluminium, are separated by an insulator sus as paper ect. For use in motors the strips are rolled together into a compact unit and placed into a sealed metal or plastic container. This may be either cylinderical or rectangular in shape and may be mounted on, in, or away from the motor. Two terminals or leads are provied for connection. The name capacitor is descriptive of the operation of the device. The capacitor acts essentially as a storage units that is,has capacity to store electricity and provides a leading current to the auxiliary or starting winding. All capacitors have this quality and all are electrically the same;they differ only in mechanical construction.     THE OIL-FILLED CAPACITOR                 This capacitor is used mainly in the permanent-split capacitor motor and for the two-value capacitor motor. The capacitor use an oil-impregnated paper as the dielectric and are permanently conne
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Starting of three phase induction motors

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Starting of three phase motors.
When the motor is in standstill position and supply is given to it, the motor works like that transformer of which the secondary is short-cricuited. Thus the rotor (sec. of transformer) will take high current and thereby the stator will also take high current from the line. The following are the disadvantage of this high current:-
    1.This may brunt the stator winding I.e. the installation may burst anywhere in the winding.
     2.It may bring the supply voltage down and due to this the relays of other motor, running near to this motor,may trip (due to low voltage). This type of voltage drop is not allowed by supply company also. Therefore big H.P. motors are provided starters to minimise the starting current.
     Motors up to 5 H.P.(A class motor upto7.5H.P.)may be connect direct to line.

      TYPES OF STARTER
The following are the types of the starter:-
    (A) Direct on line starter.
    (B) Star Delta Starter.
    (C) Auto star delta starter.
    (D) Auto transformer type starter.
    (E)Drum type or resistance type starter.

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