Feature of the Thermal Overload Relay

1. It has current setting dial. We can adjust the rated current of the motor.
2. It has trip indicator.
3. We can test the TOR (Trip On Not).

When trip the overload relay auxiliary contact point change. Therefore, cut the control circuit.

Utilization category

1) Resistive load

2) Normal motor

3) Transformer

4) Capacitor bank

Types of utilization category.

MOTOR STARTING METHOD

The starting current of 3-phase induction motor is usually 5 to 8 times the full load current or the motor. Therefore, starting when large size induction motor which are used in industry. Their starting current will cause on unacceptable level of voltage drop in the supply lines as a result this sudden voltage drop nearly will also effect the other consumer. Therefore, the supply authorities that when starting large size 3 – phase induction motors the users must adopt some starting method to reduce the starting current. Four methods are used in there.

Starting method

1) Liquid Rheostat

2) Direct on line starting method

3) Star – delta starting method

4) Auto transformer starting method

5) Rotor resistor starting method