Usually has three conditions on board needs and vehicle operation.One is the need to meet the demand of electric load, when the single load of 80% rated capacity, and the load is still likely to increase, then consider the other generator in parallel;The second is when the clearance on the docks or in and out of the narrow channel of mobile navigation state, for ship navigation safety, need two generator in parallel operation;3 it is when the need to replace with spare units running under the power supply unit, in order to ensure uninterrupted power supply, need and car to replace.

Quasi-synchronization and car way is a kind of widely used in ships and cars.In order to make the parallel operation of ac synchronous generator is stable, each parallel operation of generator must meet the following conditions:

(1) stay and phase sequence of the unit and operation unit (or power) of the phase sequence is consistent;

(2) stay and voltage of the unit and operation unit (or) grid voltage equal;

(3) for voltage and unit of initial phase and operating units (or power) in the early phase of the same voltage;

(4) to the frequency of the voltage and unit and operation unit (or) grid voltage frequency equal size.

Has when the generator set installation phase sequence of the generator to the grid phase sequence were determined, guarantee the conditions of the phase sequence is consistent.Therefore is the detection and vehicle operation and adjustment to and generator voltage, frequency and phase, to make it in the moment to meet the three conditions through the switch of generator main switch into the grid.So you can ensure that when the car is closing in and no impact current, and can maintain the stability of the synchronous running after the car.

Actual and car, in addition to the phase sequence, other conditions not possible completely consistent, and must have a certain frequency difference can quickly into parallel operation.

1, when the frequency is equal, in the early phase, voltage is not equal, two generator and car moment will produce a reactive nature between the two units of circulation, the two pressure generator.Generator in the present moment and car very small equivalent reactance, so when the voltage difference is bigger, closing moments will make a big impact current, against both generator and power system.Huge impact the impact of the current electric power, can damage the generator armature winding, the main switch contact, make the bus-bar deformation, etc.General and vehicle operation, voltage difference w shall not exceed 10% of the rated voltage.

2, stay and unit and operation unit is equal to the voltage, frequency, but in the early phase is different, the two moments in generator and car and main switch between dynamic and static contact there will be a voltage difference, there will be a lag between the two unit voltage difference of 90 ° circulation, circulation at this time is no longer the pure nature of reactive power.The active and reactive decomposition circulation, to get active component on circulation and reactive component of, under the action of active circulation, a deceleration and the other a acceleration, eventually making parallel operation of the generator to phase into the synchronous operation.Circulation of the active component of the corresponding power is called the step power, one of the advanced step generator output whole power, lag of generator power to absorb the whole step.Whole step power corresponding whole step torque, for advanced generator is resistance torque, make speed drops, for the lag of the generator is driven torque, to speed up, finally pull two machine run into the same phase synchronization.This process is known as "pull in synchronous" process.Reactive nature of circulation, the two generator equalizing effect.In order to reduce the impact current, general and operation requirements of phase difference is less than the delta S15 °.

3, weaver and equal pressure of the running mechanical and electrical, initial phase is the same, but the frequency is not equal and car.In the closing moments there will not be a voltage difference, there would be no circulation.But because the frequency is not equal, back over time, the phase difference will occur and as long as the phase difference appeared, the resulting circulation, step up the whole torque, a deceleration and the other a acceleration.As long as the frequency difference is not big, ultimately depend on the whole step torque can "pull in sync.If the frequency offset Δ f is too large, often hard to pull in sync, after closing circulation also increased at the same time, the generator and power system are bad, should avoid the happening of this kind of situation.Normally in operation and frequency offset delta f is less than 0.5 Hz, at 0.25 Hz for the best.

Generator and car, closing any moment conditions are not met, will impact current between the generating set.Impact of current plays a role of equalizing reactive component.Active component impact torque step up the whole role.As long as the impulse current is not large, is good for car and operation.If the inrush current is too large, will cause and failure, serious will cause the ship's power outage, even causes the damage of generating set.