How To Run An Inverter On A Generator

We are frequently asked how to run an inverter from a generator, IDS Engineer, Blaise Ford explains all:

The main power supply to many applications are backed up using a generator in the event that the main power source is lost. It is essential to ensure that when main power is lost and the generator kicks in that the applications which are inverter fed, power up.

When the main power supply does fail there will be a short period until the generator is ready for load. The supply from the generator will be weaker and the fault level on the generator will be lower than that of the main supply and therefore harmonic distortion must be considered which may involve derating the generator significantly. We use a rule of thumb that the generator should be de-rated by 50% for all the 6-pulse inverter load. Unless of course, you use an ABB Ultra-Low Harmonic Drive.

Some older generators may struggle to cope with the non-sinusoidal waveform associated with 6 pulse inverter loads but modern voltage regulators have less problems. If in doubt, refer to the generator manufacturer’s data. Most generators will cope with voltage distortion, but it is advised to consider some form of filtering. IDS would recommend checking with them for the most appropriate filter for the application.

Bearing in mind that starting a motor direct on-line (DOL) can draw 6 to 10 times running current levels and soft starting the motor with an inverter keeps both motor and line current below 100% of the motor rated current it is easy to see a benefit from using an inverter.

Using an inverter can reduce the load on the generator especially running a centrifugal pump or fan slower and hence, if using a diesel-powered generator, less diesel will be required. The size of the generator could potentially be reduced as the load is reduced. This can result in a large cost saving if purchasing a generator or reduced hire costs.

For more specific advice regarding how to run an inverter from a generator contact IDS experienced engineers on 0115 944 1036 or email [email protected]