AVR Of Diesel Generator Set

Automatic voltage regulator(AVR) is specially designed for matching fundamental and harmonic compound excitation or AC brushless generator equipped with permanent magnet generator excitation (PGM system).

The generator voltage regulator realizes the automatic regulation of the generator output voltage by controlling the excitation current of the generator AC exciter. The generator voltage regulator can meet the use of ordinary 60/50Hz and intermediate frequency 400Hz single or parallel generators.

What is the working principle of the generator voltage regulator?

Since the transmission ratio of the generator to the engine is fixed, the speed of the generator will change with the change of the engine speed. During the operation of the diesel generator set, the engine speed varies widely, and the terminal voltage of the generator will also vary with the engine speed. The rotation speed changes in a wide range. The generator requires a stable voltage for supplying power to electrical equipment and charging the battery. Therefore, in order to keep the voltage at a certain value, the output voltage of the generator must be adjusted.

How to repair the generator excitation system due to AVR failure?

When the excitation system of the generator fails due to AVR, or the excitation current of the generator is artificially reduced, the generator changes from sending out inductive reactive power to absorbing system inductive reactive power, and the stator current changes from lagging behind the terminal voltage to leading Run at the terminal voltage, which is the phase advance operation of the generator. The phase advance operation is also the underexcitation operation (or low excitation operation) that is often mentioned in the field. At this time, due to the reduction of the main magnetic flux of the rotor, the excitation potential of the generator is reduced, so that the generator cannot send reactive power to the system. The degree of phase advancement depends on the degree of reduction of the excitation current.

1. Reasons causing the generator to run in phase:

During low-valley operation, the generator reactive load is already at the low limit. When the system voltage suddenly rises or the active load increases for some reason, the excitation current will automatically decrease and cause phase advancement (the active power increases, the power factor increases, and the reactive power decreases. Small to reduce the excitation current).

AVR failure, failure of other equipment in the excitation system, and a large reduction in the excitation current caused by manual operation can also cause phase advance operation.

2. Treatment of the generator's advanced operation:

If the phase advance operation is caused due to equipment reasons, as long as the generator has not oscillated or lost step, the active load of the generator can be appropriately reduced, and the excitation current can be increased to make the generator out of phase advance state, and then the cause of the decrease in excitation current can be found.

When the generator cannot be restored to normal operation due to equipment reasons, it should be disassembled as soon as possible. When the unit is running in phase, the end of the stator core is prone to heat, which also affects the system voltage.

Generators that are permitted by the manufacturer or determined through special tests to be able to run in phase, if required by the system, can increase the power factor to 1 or run in a phase in allowable state without affecting the stable operation of the power grid. At this time, the operating conditions of the generator should be closely monitored to prevent loss of synchronization and restore the generator to normal as soon as possible. Attention should also be paid to the monitoring of the high-voltage factory bus voltage to ensure its safety.

Guangxi Dingbo Power Equipment Manufacturing Co.,Ltd is a manufacturer of diesel generator set in China, founded in 1974. Our product covers Cummins, Volvo, Perkins, Yuchai, Shangchai, Ricardo, Weichai, MTU etc. Power range is from 100kva to 3000kva. All genset has passed CE and ISO certification. If you have purchasing plan, welcome to contact us by email dingbo@dieselgeneratortech.com, we will guide you to select a suitable electric generator.