Electrical Equipment and Appliances
Core concepts
Know how to select and connect equipment and appliances safely, including socket outlets, lighting, fixed appliances, and motor circuits. Understand equipment ratings, IP ratings, and suitability for the environment. Know the requirements for isolation and switching, including emergency and maintenance isolation. Understand the difference between single-phase and three-phase equipment, and the need for correct polarity and phase rotation. Know the basics of appliance testing and tagging.
Traps in questions
Questions often test whether an appliance is suitable for a wet or dusty area based on its IP rating, or whether a particular appliance requires a dedicated circuit. Candidates confuse isolation with switching, and forget that a plug and socket can serve as an isolator under certain conditions. Another trap is phase rotation on three-phase motors and the effect of reversing two phases. Be careful with the difference between double-insulated and earthed appliances.
Worked example
A three-phase motor is installed on a machine. Before connection, confirm the supply phase rotation matches the motor's required direction. If the motor runs backwards, swap any two of the three supply phases. Confirm the motor's rated voltage and current, and ensure the overload protection is set to the motor's full-load current.
Rule of thumb
Match the equipment's IP rating and electrical rating to its environment and load. Always isolate and prove dead before working on equipment.