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How to Check Engga Generator End Before Operation

Aug. 24, 2018

In order to ensure the reliability of the operation, it is absolutely necessary to carry out mechanical and electrical inspection before operation after the generator is transported, stored, installed and equipped.

How to Check Engga Generator End Before Operation.jpg


1. Assembly Inspection


①The coupling between generator and engine requires that the parallelism and concentricity of coupling should be less than 0.1mm, which will affect the normal operation of bearings and lead to damage. The coupling condition should be re-measured before installation.


②When installing the generator, make sure that the cooling air is free from the entrance, and avoid reentering the generator from the hot air.


③All bolts and screws have been tightened, especially the rotating parts, and the guard covers and mesh covers are installed in the correct position.


 Look closely inside the generator. No foreign bodies exist. If the surface area of the coil or rotor has dust, it can be blown off by dry compressed air or by hand bellows. With hand or other tools slowly rotating the rotor, should be flexible rotation without any rub and so on.


2. Check the insulation resistance of stator windings


The AVR must be disconnected at this point.


Measure insulation resistance with 500 V meter or other similar instrument. First, the grounding conductors between all neutral lines and earthing lines are disconnected, and then the ground insulation resistance of UGV W at the end of the wire is measured in turn. In cold state, the resistance value should be greater than 2MΩ. A lower than 2m Ω indicates that the winding is wet, dirty, or short-circuited to the ground. Since the generator coil has been subjected to voltage resistance test during the production process, repeated voltage resistance test will lead to the reduction of insulation life. If a voltage test is required for customer approval, the test voltage should be reduced to 0. 8 (2 × rated voltage 1000) / 1440V.


The insulation resistance of the winding can be restored by the following methods:


a. Dry the generator in a 110C oven for 24 hours (without AVR).

b. The hot air is blown into the inlet of the generator and the generator operates without the magnetic field of the exciter.

C. The dehumidifier can be used for electric drying.

D. Main stator short circuit method (not connected with AVR).)


3. Check ground wire


The earthing bolts on the generator base and junction box should be effectively grounded, and the earth wire should have sufficient cross-section and should be connected with buried water pipes or metal plates buried deep underground to ensure good grounding.



Minimum grounding Line Cross Section area (mm2)







4. Check wiring


The internal wiring of generators, exciters, and automatic voltage regulators is connected before leaving the factory. Before operation, check again whether the contact points are reliable or not, whether the connection between generator and control panel is correct.

Check whether the connection between the cable terminal and the line is correct, safe and reliable.

Check whether the cable is damaged or not. Loose, ensure that it is correct, the joint nut tightening not loose, good contact.


According to the schematic diagram or wiring diagram, select the appropriate power cable, use copper connector to connect, copper joint and bus, bus and bus after consolidation. The local clearance at the joint should not be greater than 0.05 mm, the distance between conductors should be greater than 10 mm, and the necessary grounding wire should be installed. The winding connection should correspond to the operating voltage. Generator main outlet wire technical requirements, 3 A per square, from the motor to the control box and control box load.


In order to ensure safety, each of the above must be carefully checked until all comply.



5. Test adjustment before operation


Generator excitation system, before the factory has been adjusted with the subordinate generator. Host factory state is star connection, frequency of 50Hz, line voltage of 400V.



6. No-load adjustment

Start the prime mover and speed up to rated speed. During this process, the generator should be able to build voltage by self-excitation and the voltage value should be close to the rated voltage. A slight deviation can be adjusted by spinning the voltage trimming potentiometer in the AVR or on the control panel. In the course of adjustment, attention should be paid to whether the generator voltage is stable, whether the three-phase voltage is balanced, whether the generator unit is running quickly, and whether the sound is harmonious.


7. Check output

In the rated speed of the unit and the generator in the no-load state, the voltage at the end of the generator is rated voltage, or close to the rated voltage, and the three-phase balance is obtained. At this point, the current of the exciter is in accordance with the number on the nameplate (or approximately), all excitation windings, main windings, and rotary diodes are considered to be in good condition.


8. load regulation


Close air switch to maintain load power factor of 1 and 0.8 (lag), respectively. Gradually increase the load to full load, and then gradually reduce the load to no load. In this process, the steady-state voltage adjustment rate of the generator should not be greater than the specified value. Observe whether all the indicating instruments on the control panel are normal.Check whether all parts of the generator are overheated. The generator can be put into normal operation after the satisfactory results of both no-load and load debugging.



Note: The plug of the automatic voltage regulator (AVR) should be unplugged when the prime mover needs to run at low speed for a long time so as not to be damaged by the overload of the automatic voltage regulator and the excitation windings for a long time.




① Leave the output air switch open.

② Start the prime mover and gradually increase the speed to the rated speed. (Note: the acceleration should not be too long).


Note: After the diesel generator is installed, the initial use of the generator can not immediately add load, it has to go through a few hours of no-load operation, observe the situation and dehumidification, and so on. The operation is stable and reliable, the load can only be loaded from 30% to 50%, and the running time of each section is about 1 hour. If it is found that there is no abnormal phenomenon before the trial operation, pay attention to temperature rise, vibration are good, can run for a long time.


③ Turn on the output air switch and load, put into normal operation.




①Reduce generator load.

②Disconnect the output air switch.

③Stopping prime mover



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