New Generation Voltage Regulators

When output current of the alternator drops near zero, the voltage at the tap does also, allowing the voltage regulator to sense and signal this condition.

Bus low sensing and indication
A "bus-low" condition exists when the voltage on the bus falls below a specified limit such as 12 volts, on a 14 volt system, and 24 volts, on a 28-volt system. This indication is that the aircraft system load exceeds the alternators output and insufficient voltage is available to replenish the battery. Worse, the aircraft may now be using the battery to support the system. Extended "bus-low" operation will deplete the battery. Load shedding may be required to alleviate this bus-low condition.

This system behaves in a manner similar to the alternator out circuit with the difference being that the input signal source is usually contained within the regulator with only the input from the lamp remaining outside. However, before replacing the alternator or a regulator, check the lamp circuit in the same way you would with the Alternator Out circuit.

Through the years, we have learned that the key to solving many electrical system problems is education and patience.

If you run into to a situation which has you chasing your tail there is expert help available. Please feel free to contact Electrosystem's Dave Eisenstadt or Kevin Grant at 334-227-8306.