Generator Care Generator Maintenance

Generator Voltage Fluctuation – What’s its Causes and How to Fix It

When the generator engine starts, the engine takes a few minutes to start and then stabilizes the speed even after connecting the load. But, if the voltage readings keep fluctuating or the connected lights and screen flicker, there is a problem that you need to troubleshoot, starting with understanding what causes generator voltage fluctuation.

The common cause of voltage fluctuation is a problem in the generator engine, such as wavering engine speed or governor issues. It could also be caused by loose connections, worn or torn cables, or the Automatic Voltage Regulator problems.

It’d be best to understand these problems, their causes, and how you can fix them to troubleshoot the voltage fluctuation fully. In this post, I have covered each of these issues separately to smoothen the diagnosis and offered the most appropriate way to fix the problem.

What Causes Generator Voltage Fluctuations & How Do You Fix It

We all know how handy a generator can be during an outage. However, it won’t serve its purpose if the voltage keeps fluctuating.

What’s generator voltage fluctuation?

Generator voltage fluctuation is when its voltage output keeps changing, going up and down without any stable value. You can tell your generator voltage is fluctuating by checking the unit’s voltmeter for unstable readings if yours has it, or check the lights and lamps in your home for flickering.

Voltage Fluctuation is dangerous. The unstable voltage output can:

  • Fry your electronics,
  • Cause damages to appliances, and
  • Cause repeated nuisance breaker tripping
  • Shorten the generator engine life.

That is why the fluctuation cause needs to be identified and fixed as soon as possible. It’d also be best to disconnect your appliances and electronics from the generator when its voltage output fluctuates.

Here are the common causes of unstable generator voltage and how you can solve them.

1) Generator Engine Problems

An engine is the heart of a generator. If something was to interfere with its operation, it surely affects its outputs, one being voltage. Here are two ways the engine problem can cause voltage fluctuations.

a) Engine Speed (RPM) is Unstable

The generator engine speed, referred to as engine RPM, has to stay stable for the generator to produce stable voltage. If the generator engine runs high-low without any stability, there will be fluctuation.

The best way to troubleshoot unstable engine RPM is to pay attention to the engine sound when it’s operating. A stable engine will have the normal noise, but a fluctuating one will instantly rise and drop.

If your generator engine noise isn’t what you’re used to, the engine’s rotation speed is unstable. You can get yourself a tachometer and ensure the generator engine is running at 1500 RPM. You might also get 1800 rpm at 50 Hz or 3600 rpm at 60 Hz.

If your unit’s speed is not normal, it will tend to shift way high above 1500 RPM and way low 1500 RPM, which will be the source of your generator voltage fluctuation.

What causes unstable generator engine speed?

Your generator engine speed will fluctuate when:

  • The fuel is dirty, clogged, or missing.
  • You’re using slightly stale, dirty, or water-compromised fuel.
  • Your generator fuel is nearing empty, and you placed the generator on a slope so that the engine is getting an uneven supply of fuel because of the vibration.
  • The fuel line is clogged with debris or pinched and leaking.
  • The fuel regulator is faulty, especially if the governor or Electronic fuel System automatically regulates your unit’s fuel system.

What is the best solution(s) for unstable generator engine speed?

You can make sure your generator engine runs at stable speed by:

  • Keeping the air filter clean or replace it if over clogged
  • Making sure you always use ‘good’ and clean fuel with no signs of stale. If you’re using fuel from storage, make sure it’s not more than two weeks old and was treated with a fuel stabilizer before storage.
  • placing your generator on level ground when it’s running, always
  • Inspecting to see the fuel is flowing smoothly and there are no leaks before starting your generator, and
  • Inspecting the automatic fuel regulation system to rule out any problems

b) Generator Governor Problems

A generator governor controls the fuel supply at the carburetor to automatically reduce or increase the engine speed concerning the connected load. It also reduces the engine speed when the rotation exceeds the rated RPM to protect the generator engine.

If it were to malfunction, it could cause unstable engine speed and the generator voltage fluctuation.

It’s tough to DIY a governor problem since you have to inspect the governor itself, the actuator valve, or MPU for issues. You want to make sure they are in ‘good condition and operate automatically and properly to control engine speed.

If the fuel line is clean, the fuel tank is above half, and there are no fuel leaks, your governor might cause unstable engine speed. In that case, it’d be best to take it to a qualified technician to diagnose it.

2) Problems with the Generator

If the engine speed is stable, but the voltage is fluctuating, the problem is caused by an electrical problem in your generator. It can be caused by:

a) Worn Out Output Cable

The generator extension and wiring connecting it to the inlet box might cause voltage fluctuation. Worn-out insulation could leak voltage to the ground and cause a voltage drop.

Normally, a GFCI outlet would trip when it detects such a fault. But if your generator doesn’t have one or you’re using an outlet that doesn’t have one, you will get fluctuating voltages.

Inspect the generator extension cable for wear and tear. Try to feel for breaks inside the insulation – they can also cause fluctuation if the broken points are touched momentarily. If it’s broken or worn out, get a high-quality, durable extension cord that won’t fail you shortly.

b) Loose Connections and Terminals

If the extension cable is all new and doesn’t seem to leak, there could be loose connections and terminals, which can also cause voltage fluctuations.

Inspect all the connections to the generator to make sure the connections are tight and snug. Loose connections will cause the charges to flow in unstable quantities and contribute to the unstable voltage output.

All terminals between the generator and the load must be tight to give enough contact between the terminals. Make sure there is no soot between the terminals caused by repeated short circuits when they move.

Don’t forget to check the generator breaker connections, the AVR terminals, and the governor connecting rode.

Problems with the AVR Generator

If everything stated above seems to be working right or in ‘good condition,’ the cause of your generator voltage fluctuation might be a faulty AVR, automatic voltage regulator.

The automatic voltage regulator’s main purpose is to regulate the generator voltage output and keep it stable. If it were to fail, your generator would produce no power, or its outputs will fluctuate.

What are the causes of AVR failure?

Unstable Engine Speed: if the generator engine speed is unstable, the rising and dropping can easily compromise the AVR sensors and controllers.

Generator Overloading: when you connect a load to a generator, the engine runs harder to try and match the power draw. The same effect goes to the AVR as it tries to stabilize the voltage output. When you add more load, more strain is put on the generator engine and the AVR. If you overload the unit, you not only risk damaging the generator engine but also the AVR as it goes way above its limit to stabilize the out-of-limit voltage.

Short Circuit: if your generator was to experience a short circuit, the fatality could cause damages to your genset and its AVR. Resistance surges can act on the AVR capacitors and other components.

How can you prevent AVR failure?
  • Ensure your generator runs at stable speeds all the time. If you suspect the engine is running at unstable speeds, unplug the load and shut it off before it can cause damages.
  • Avoid overloading your generator. A lot can go wrong when you try to power a load that the generator cannot handle.
  • Avoid short-circuiting the generator. Keep off the electrical line if you have no experience. Get a qualified electrician to do generator installation, upgrades, and repairs.

Related Questions

Can a UPS Help During Voltage Fluctuation?

Inline interactive UPSs features technology designed to correct minor voltage fluctuations, mostly under or overvoltages, without switching to battery. They use autotransformers designed to regulate the low voltage changes. But, when there is a considerable voltage fluctuation, the UPS will annoyingly keep switching to and out of the battery.

About the author

Sharif Gen

Leave a Comment