Direct OnLine Motor Starter, Basic For Beginners.

What is Direct On-Line motor starter?
Considered the most simple motor starter option, Direct on Line or D O L is a full voltage motor starter. Through a switch or a contactor, this starter instantly connects a motor to the power supply.
This full voltage connection, can cause the motor to draw an inrush current of 5 to 8 times of its normal operating current, making D O L starter generally applicable with low rated motors, under 5 hp or 4kW.
This type of starters, are commonly used to start small domestic water pumps, conveyor belts, fans, and compressors.
There are three main components needed to build a D O L starter. Number 1, Molded Case Circuit Breaker or MCCB. This is use to manually connect and disconnect the power circuit of the starter to the main supply. This also serve as a protection, to trip, or isolate a circuit from excessive high current due to a short circuits from a line to Line, or Line to ground faults. Preventing farther damage to other part of the system.
Two, a contactor is an electro-mechanical device, operated by an electric coil that allows automatic and remote switching to start or stop an electrical equipment.
Three, Overload relay. this is a protection device that prevent motor burns or damage, by monitoring the current of the motor circuit, and breaking the circuit when an over current being drawn by the motor is detected.
The secondary components are control devices, its requirements varies depending on the application of motors, which are driving the equipment.
For this lecture, we use a Start and Stop push buttons with momentary held contacts. Miniature Circuit Breaker or MCB, and a step down transformer for the control circuits.