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What is Power Factor Lagging and Lead of Generator Set?

Jul. 11, 2019

Due to some users ask Starlight Power manufacturer about lagging and lead of generator set question, today Starlight Power Manufacturer shares with you.


What is generator power factor lagging?

In alternator current, based on voltage, the phase angle of current lags behind the phase angle of voltage, which is called current lagging behind voltage. COSф of voltage and current lagging angle is power factor, because current lagging behind voltage is lagging power factor.


Lagging of a generator is a common phenomenon, which indicates that the phase of current lags behind the phase of voltage, indicating that the circuit is inductive and the load of generator is the main type.

Ricardo diesel generator 

What is generator power factor lead?

Only in circuits using capacitive elements, the current will exceed the voltage. Lead, is a rare case, indicating the current phase lead voltage phase, indicating that the line presents capacitance, load capacitance is too large,usually the capacitance compensation is over. Capacitance is rare in normal load. Power factor lead usually cause unstable phenomena in the power grid, easy to generate oscillation, which is prone to shocks and grid faults. Therefore, it is necessary to avoid the occurrence of power factor lead as far as possible.


In generally, the power factor of generator is 0.8lag. The normal working state of the generator is that the power factor is positive, or called lagging. At this time, the excitation current is large and the generator is in the over-excitation state, which sends out active and reactive power to the system, to meet the needs of the power grid for inductive reactive power; If the power factor becomes 0.8 lead, it means that the system does not need the generator to generate reactive power, but needs the generator to absorb reactive power. At this time, the excitation current is small and is in under-excitation state.


What cause power factor of generator lead?

Overexcited synchronous motors (elevators) and capacitive loads can cause leading power factor, where current leads voltage. If not controlled these can lead to loss of voltage control and possible damage to the generator.


Power factor lead will cause come problems, as follows:

1.Increasing of line power loss.

Line power loss is showed to square of line current x line resistor and if power factor make to lead with unnecessary capacitor installation, power loss will be increased more by current increasing same as lagging power factor.


2.Increasing of transformer power loss.

Transformer power loss will be increased with serious heating by current increasing same as line power loss.

3.Increasing of system voltage.

Leading reactive current which is on capacitor for power factor improvement and cable in light load make to increase a voltage at line reactance application. 

Picture of 3 phase power factor meter

How to deal with generator power factor lead problem? 

1.Check the current coil wiring of power factor meter. If the “U” phase is connected to the wiring post 6 incorrectly, we should change current coil wiring of power factor meter.

2.Check the voltage coil wiring of power factor meter, if connect “ V” phase wiring to “3” wiring post, connect “ W” phase wiring to “1” wiring post incorrectly, we should change voltage coil wiring of power factor meter.

3.Check connection phase sequence of power factor meter, if its connection has not meet the requirement, we should change voltage phase sequence of power factor meter.

Starlight Power diesel generator for sale covers brand: Cummins, Perkins, Volvo, Deutz, Yuchai, Shangchai, MTU, Weichai, Doosan etc. If you are interested, please contact us by email sales@dieselgeneratortech.com, we will work with you. 

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