The amp clamp is used for measuring current flow through a wire. The use of the unit for aircraft troubleshooting is limited to three phase power applications.

The general rule for clamp operation is to isolate ONE wire only. The unit is not accurate when placed around two or more wires.

Comparison of the three power input legs on fuel pumps and electric actuators can help with verifying a missing or low current leg.

Quick Notes on Three-Phase Power

1. All three phase power from the engine driven generators to the distribution busses is monitored with CT's or current transformers. Any imbalance measured will cause the automatic disconnection of the affected system.
2. Most aircraft devices that require high three phase power are also monitored with CT’s. Imbalances that exceed a predefined limit will usually cause the device to be disconnected from the power source.
3. Some manufacturer installations for three phase motors do not use CT’s. A single, three phase circuit breaker is used for control. Open or low leg(s) will cause the current draw on the good leg(s) to go up, resulting in the breaker popping.
4. EXTREME CAUTION should be taken when working with power wires. 115VAC/400Hz should always be treated with respect.

THE INFORMATION PRESENTED ON THIS SITE IS TO BE USED AS A GUIDE.

APPROVED AIRCRAFT MANUFACTURER MAINTENANCE MANUAL PROCEDURES SHOULD ALWAYS BE FOLLOWED.