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What are the Causes of Diesel Generator Under Voltage?

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Diesel generators are a wise investment for residential properties and businesses. Their ability to supply seamless prime and standby power reduces the risk of disruptions and maintains productivity. Diesel generators are generally highly reliable but not completely immune to faults.

Noticing an issue with your generator can be disconcerting, but these issues are usually easy to fix. One of the most common faults is when diesel generators issue an undervoltage alert.

In this guide, we’ll reveal how to identify why your diesel generator’s performing undervoltage and how to fix it.

What does diesel generator undervoltage mean?

In simple terms, a diesel generator showing an undervoltage warning means it performs at an output lower than expected. Failing to protect the generator can cause long-term damage, limit the generator’s lifespan and cause safety hazards, including:

  • Equipment Malfunctions: Any devices the generator powers could malfunction due to the low voltage. For example, machinery might be unable to operate, and the lighting system could fail to generate electricity.
  • Appliance Damage: Devices connected to a poorly performing generator can also suffer damage, although this rarely happens unless the under voltage is extreme.
  • Sudden Shutdowns: Most diesel generator models have a control panel that allows you to collect data. Sudden shutdowns could compromise this data or delete it completely.
generator repair

The most common causes of generator undervoltage issues

Diesel generators power large-scale operations and are always there when you need them. So, with all this responsibility, it’s easy to see why voltage issues can happen. Let’s explore the potential causes of these overloads so you can deal with the problem and prevent costly replacements.

Voltage regulator malfunctions

Voltage regulators ensure your diesel generator operates safely while maintaining a consistent voltage output. When they’re at their best, regulators can reduce the risks of undervoltage, but when they fail, they can’t adjust the excitation device, which can cause malfunctions.

Disruptions in the voltage-regulating signal mean it can’t adjust excitation currents. A rarer cause of regulator malfunctions is when the component becomes stuck and restricts the excitation output line from producing a strong current.

The fix

When dealing with regulator issues, it’s best to call a professional diesel generator repair service for support. Specialists know how to safely replace and calibrate voltage regulators without damaging the generator.

Load issues

Your generator’s maximum load capacity determines how much power it can deliver. When you connect multiple devices at once, you risk exceeding the maximum load capacity, causing undervoltages.

While minor overloads cause slight voltage decreases, severe overloads can damage the generator and strain your equipment unnecessarily.

The fix

Prevention is more effective than cure, and minor overloads don’t usually cause long-term damage. Know your generator’s maximum capacity and ensure you protect the diesel engine and other components.

Generator alternator replacement

Voltage sampling line disruptions

Faulty voltage sampling lines can send inaccurate information to the voltage regulator, resulting in poor responses. For example, if there’s a disruption or loose connection, the regular might believe the voltage output is too low or high, and its response could cause damage.

This can mean an undervoltage or overvoltage fault occurs, potentially causing damage to the diesel generator.

The fix

In some cases, a technician can repair loose connections in sampling lines or take steps to reduce the risks of interference. They might also need to replace faulty wires, but the technician will first check for other potential causes, as sampling line errors are rare.

Varistor or rectifier bridge diode damage on generator winding

The varistor and rectifier components play vital roles in ensuring the voltage system operates safely. While varistors prevent surges and provide undervoltage protection, the rectifier bridge diode supports the AVR (automatic voltage regulator), ensuring a consistent output voltage.

Damage to these components can indirectly cause undervoltage warnings, restricting your generator’s performance.

The fix

Rectifier bridge diodes and varistors are sensitive components, so it is best to seek professional support. If these components need replacing or fixing, a specialist can perform the work.

Speed fluctuations

A diesel generator’s voltage output closely links to the engine’s speed. Slow speeds can cause undervoltages, while high-speed fluctuations confuse the regulator, making it hard to maintain a consistent speed.

The fix

Speed issues often occur due to load issues or faulty governor systems. You can address overloads efficiently, but a repair service will need to fix the governor.

Meccalte Alternator

Fuel problems

Diesel generators can only function with compatible fuel, and any issues with the fuel system can impact their performance. Forgetting to fill the generator up, problems with the tank, and not using the right fuel restrict the engine’s ability to produce consistent power.

The fix

Your chosen generator will recommend which fuel to use, and fuel services can help you remove any contamination from old or incompatible diesel.

Three-phase grounding issues

Three-phase grounding is vital in ensuring the generator’s safe operation, and any malfunctions can cause a voltage issue. A ground fault disrupts the current flow and causes the voltage to become unstable, but grounding malfunctions also occur when they’re connected incorrectly.

The fix

Reviewing your generator’s manual and determining whether you meet the grounding recommendations is important. General maintenance can prevent grounding issues, but a major fault can cause long-term damage.

Final thoughts

Diesel generators rarely experience significant issues, and most are simple to fix. Choosing a diesel generator set from a reputable supplier gives you peace of mind that you’re investing in quality. We also offer an installation service, ensuring all components are connected correctly.

If you’re ready to streamline your power needs and look forward to the many benefits diesel generators offer, please feel free to contact our sales team today. A specialist will discuss your needs and advise on suitable models.

Paul Phelps Solar Power Owner
Paul Phelps
Paul is the MD of Solent Power and specialises in emergency power solutions, helping to protect your facilities from power loss. Get in touch with us today to discuss the different power brands that we can offer and how they can suit your needs.
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