![]() ![]() Overload is also the type of over current. Thermal overload protection is a type of security when the motor draws over current or excessive current and causes overheating of the equipment. Green and Red or start and stop buttons control the contacts. The DOL starter comprises an MCCB or circuit breaker, contactor and an overload relay for protection. ![]() A direct online starter consists of two buttons, a GREEN button for starting and a RED for stopping purpose of the motor. The wiring diagram for a DOL stater is shown below. However, for large-rated motors, we can use an oil-immersed DOL starter. If we connect a large motor directly across 3-phase line, it would not run smoothly and will be damaged, because it does not get accelerated as fast as a smaller motor since it has short axial length and larger diameter more massive rotor. Therefore, small rating motors smoothly run when it is connected directly to a 3-phase supply. Hence, speed increases and thus the value of armature current decreases rapidly. In a small rating motor, the rotor has a more considerable axial length and small diameter. ![]()
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