Understanding Load Bank Tests Used on Generators

Load tests are vital elements of diesel generators. However, unless you are technically minded, it is likely that you do not know what they are or what they do. This is why it is important to really start with the basics and effectively taking a bit of a lesson, attempting in so doing to avoid any technical jargon.

Before starting, however, it is also important to know that HIPOWERSYSTEMS carries the best diesel generators, should you wish to use one.


Although jargon will be mostly avoided, it would be useful if you have taken some classes in school about electrical sciences, or that you have worked in an environment that allowed you to build at least some professional or practical experience.

About Loan Bank Tests

Basically, a load bank test is a type of sequential procedure that shows how a generator is performing when exposed to different loads of power rating. This is expressed in low, medium or high percentages. Usually, a diesel generator (DG) will gradually be subjected to increasing or decreasing loads in a facility, so that proper studies can be conducted.

Obviously, the most important part of the test is performance at between 50% and 90%. This is where most usage is going to be, so this is where it is most important that the DG functions properly. If it does, then it is safe to assume it can also handle lower loads. A DG that has never performed to at least a 30% load should always be tested before use.

A load is basically the electrical resistance that exists within the piece of equipment that is being tested. This includes drained out batteries and cables that will use the DG in order to obtain power. Within modern facilities where load tests are conducted, experts will simulate real life situations. For instance, they will use variable loads across the full range of possibilities, gradually changing from one to the other, instead of making abrupt changes.

Sensors are used to record and monitor a number of different parameters. These include:

  • The vibration;
  • The engine torque;
  • The pressure;
  • The temperature;
  • The quantity of leftover fuel;
  • The fuel usage;
  • The horsepower delivered; and
  • The length of time a generator can operate successfully at peak load.

All these measurements are recorded using a computer system. This is able to create graphs depicting the different variables and a user can indicate which one or ones they are most interested in. They can then compare the graphs that demonstrate actual performance to the graphs of desired or expected performance. They can then calculate how much the DG deviates, allowing them to then look at the elements of the generator that could be causing this deviation. This is particularly important on rental generators, or generators that are sold on as refurbished.

If you were to purchase a second hand DG, it is likely that you will receive a copy of the load test report for your information.

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