Alternating Current and AC Equipment
AC Generator Troubleshooting Guide Aside from these basic checks, some more advanced procedures are found in the following checklist. These additional checks are too advanced for most beginners and will have to be carried out by a trained technician, preferably one certified on your particular brand of generator.
Low Voltage
Check the voltage at the generator. If the reading is OK and your panel meter is reading low, there is an excessive voltage drop in the wiring between the generator and the panel.
If the frequency is erratic with all loads turned off, check the governor for proper operation. Can you hear subtle rpm changes?
High Frequency
Have the governor operation checked.
Low Frequency
Turn off all loads. If frequency returns to normal, the generator is being overworked and is probably underrated. Either give up some AC toys or prepare to upgrade to a bigger generator.
Check for faulty governor adjustment.
Verify correct generator engine rpm and governor settings.
Galvanic Isolators
Check all connections and wire terminations for integrity. First make sure the generator is off!
If voltage is OK until the engine warms up and loads are applied, the generator voltage regulator and related circuitry are at fault.
The voltage regulator may need adjustment or replacement.
A device that has become increasingly popular in recent years on new boats is the galvanic isolator. The trouble with them is that most folks, including many marine electricians, haven’t the faintest idea what they do. So, what are these things used for anyhow? Well, here’s the definition: “A device installed in series with the green grounding conductor of the shore-power cable which effectively blocks galvanic current flow (DC), but permits the passage of alternating current (AC).” You’re probably still wondering, Yeah, but what does it do? Why do I need one? If you spend much time at the dock plugged into shore power, you need a galvanic isolator. Here’s why: Galvanic current flow is a danger at any marina, putting your boat at risk of galvanic corrosion. The more boats with AC shore power, the greater the risk. Your boat could be in great electrical shape, but once plugged into shore power it becomes electrically connected to its neighbors via the green grounding wire in the AC system. This connection completes an electrical circuit between multiple boats, each with potentially dissimilar underwater metals exposed to the surrounding seawater. What’s created is a giant battery and the potential galvanic corrosion that can result. Further, it is also possible to transfer higher-voltage DC stray current from one
High Voltage
Check the frequency for normal range (between 57 and 63 Hz in the United States).
If possible, adjust the voltage regulator.
Verify correct engine rpm and governor adjustments.
Erratic Voltage
The generator brushes could be worn or burned.
There could be internal wiring problems or loose connections.
Erratic Frequency
Check for loads cycling where the generator turns the current on and off.
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