Generator Under Voltage – Causes – Helpful advice to fix the issue
Generator under voltage can occur suddenly without warning. Key causes of under voltage include:
- Blown voltage-sensing fuses—check, clean, and replace them as needed.
- Failing capacitors that regulate voltage; inspect and replace if necessary.
- Malfunctioning Automatic Voltage Regulators (AVR)—require a professional for adjustment.
- Alternator issues—check diodes, perform a Megger test, and ensure connections are secure.
- Physical signs of damage like rust or cable breaks; perform a Megger test on-site. After identifying and resolving the root cause, the issue should not recur. For further guidance, consult various resources from Power Continuity.
Diesel Generator under voltage can happen suddenly, without warning.
Possible causes of Generator Under Voltage
Immediately check the following to isolate the root cause:
- Firstly, check all voltage-sensing fuses to ensure that none of them have blown.
- Secondly, take out each fuse, visually check for issues, clean and replace. Ensure firm fit.
- Check capacitors if you generator has any capacitors.
- Functions of the capacitor are to induce voltage into the rotor.
- A capacitor regulates voltage.
- An old or failing capacity can cause a low voltage reading on the generator control panel .
- Ensure that the AVR (Automatic Voltage Regulator) is fully functional otherwise replace the AVR if necessary.
What is the AVR
The AVR controls voltages, so this is often the major reason for generator under voltage issues. This requires a generator engineer and a laptop to plug into the system – call your dealer. Once on the engineer can make adjustments to the AVR to stop the generator under voltage. Parameters will be adjusted to eliminate the under voltage issue.
What is the AVR
- Check alternator diodes and Megger test the alternator windings to highlight any issues.
- Visually check for loose electrical connections.
- Physically touch the connections/terminals for any movement and reinsert any that are loose.
- Has there been any water damage to the alternator?
Signs of age and rust
- Finally, check for rust, damage, cable breaks or copper showing.
- Carry out a Megger test and see if you can induce generator under voltage whilst on site.
Generator Under Voltage can occur randomly although the root cause will be one of the above. The above tests should highlight the cause and therefore enable you to fix the problem. Once you have isolated which of the above has caused the issue and then fixed the problem, it should never occur again.
- Also, for more helpful information read more advice on the following Power Continuity Knowledge Resource:
www.powercontinuity.co.uk/knowledge-base/generator-frequency-fluctuation/
www.powercontinuity.co.uk/knowledge-base/generator-hunting-and-surging/
www.powercontinuity.co.uk/knowledge-base/generator-avr-what-is-the-avr/
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