SOLUTION

• Interlocks are nonmanual control switches activated by an unsafe condition.
• Interlocks do operate automatically but are not intended to control the motor in normal circumstances.
• Typically, interlocks stop motors automatically but do not start motors automatically.

A few examples of interlocks are

• Motor overloads
• Low level on the suction side of a water pump
• High discharge pressure on a positive displacement pump
• High torque on a conveyor belt

Interlocks are intended to protect human life or equipment, so they are designed to function regardless of whether a manual or automatic control is in use. Therefore, they are wired in a motor control circuit on the line side of other devices.