CSLB C-10 Electrical ContractorSafety and TestingMedium
A technician is installing a new 480V, 3-phase motor. During the pre-energization checks, they need to confirm the correct phase rotation to prevent damage to the motor. Which instrument is designed for this specific purpose?
- AContinuity Tester
- BPhase Rotation Meter
- CVoltage Tester
- DInsulation Resistance Tester
Show answer & explanationAnswer & explanation
Correct answer: B. Phase Rotation Meter
A phase rotation meter is a specialized instrument used to determine the sequence of phases (A-B-C or C-B-A) in a three-phase electrical system. This is crucial for motors, as incorrect phase rotation can cause them to run backward or suffer damage.
Why the other options are wrong
- A. A continuity tester checks for a complete circuit, not phase sequence.
- C. A voltage tester checks for voltage presence, not phase sequence.
- D. An insulation resistance tester measures insulation integrity, not phase sequence.
Phase Rotation Meter
An electrical test instrument used to determine the correct phase sequence (rotation) of a three-phase power supply. This is critical for ensuring proper operation and preventing damage to three-phase motors and other rotational equipment.
- Identifies clockwise or counter-clockwise phase sequence.
- Essential for 3-phase motor installations.
- Prevents reverse rotation and potential damage.
Memory trick: For Rotation, Use the Rotation Nation!