What to do if the voltage is too low?
Check the speed. If the speed is too low, increase the speed (to the correct value, then adjust P2 of the AVR); if the speed is correct, check the following 4 items: a. Check the AVR wiring (possibly AVR failure); b. Short-circuit of the Excitation field winding; c. Rotating diode burned out; d. circuit Opening of main rotor winding (check resistance)
The generator is significantly injured, What cause the noise and vibration?
a. The system is shorted.
b. parallel error.
c. The coupling is broken or damaged.
d. The shaft end is broken or damaged.
e. Deformed or shorted rotor.
f. The fan is cracked or loose on the shaft.
What is the reason for the obvious vibration of the generator and the obvious noise in the motor?
a. Three-phase load imbalance
b. Stator short
What is the reason for the generator vibration?
a. Poor alignment (coupling) or vibration of the prime mover.
b. Rotor balance is unqualified (primary motor --- generator)
What causes the generator base to overheat ( 40 ° C above ambient temperature)?
a. The air passage is blocked or the hot air is repeatedly circulated to eliminate the air passage obstruction
b. The generator operating voltage is too high (greater than 105% of the rated voltage under load)
c. The generator is overloaded.
How to find the fault when the bearing temperature is 50 ° C higher than the ambient temperature?
If the bearing turns blue or the grease turns black, replace the bearing.
What are the ways to dry the generator?
a. Cold operation
If a normal generator has not been running for a long time in a dusty, humid environment. The wires on the AVR board should be disconnected and insulated ，then run the generator. About 10 minutes, this may be enough to dry the winding surface, increase the insulation resistance value to more than 1.0MΩ, remove the DC power supply, and reconnect the exciter magnetic field leads "F +" and "F-" to the AVR terminal on. Restore the unit, put all covers back on and try again.
b. Air introduction and drying
Remove all covers from the generator to allow the escape of humid air. During the drying process, the airflow should be able to circulate freely within the generator and take away moisture.
Please use two 1-3KW hair dryers to blow hot air from the generator inlet.Note that the distance between the heat source and the winding should be kept at least 300mm to avoid the damage of winding insulation caused by overheating. Keep heating and record the insulation resistance every half an hour. When the value reaches the value specified in the section "typical drying curve", the drying process is completed. Remove the heater, cover all covers, and try again. If the unit does not operate immediately, ensure that the generator is equipped with a space heater and energized. The insulation resistance should be tested before the next operation.
Short circuit method
Note: this process must be carried out by a qualified engineer who is familiar with the safe operation procedures of the generator set.
First, carry out all mechanical and electrical safety operations related to the unit and the site to ensure the operation safety on the generator.
The output end of the generator should be short circuited with a short-circuit piece which should be able to withstand the rated current of the generator.
Disconnect "F +" and "F -" on AVR.
Add a DC power supply (F + is connected to the positive pole and F - is connected to the negative pole) between the conductors "F +" and "F -", the DC power supply must be adjustable within 0 ~ 24V and can be provided at most Two Ampere current.
Connect a suitable AC ammeter to detect the short circuit current.
First adjust the DC power voltage to zero, and then start the generator set. Increasing the DC voltage slowly to make the current flow into the field coil of the exciter.
When the excitation current increases, the stator current in the short circuit state will also increase. The stator current must be monitored so that it does not exceed 80% of the rated current.
Every 30 minutes, perform the following tests:
Stop the unit, disconnect the external excitation DC power supply, then test and record the insulation resistance of stator winding and make a chart. The measured figure should be compared with the typical curve. When the insulation resistance value reaches the value specified in the section "typical drying curve", the drying process is completed.
Once the insulation resistance reaches 1.MΩ, the DC power supply can be removed, and the field leads "F +" and "F -" of the exciter can be put into trial operation again.
If the unit does not operate immediately, ensure that the generator is equipped with a space heater and energized. The insulation resistance should be tested before the next operation.
Important! Do not short-circuit the three-phase winding when AVR and generator are connected. When the current exceeds the rated current of the generator, the winding will be damaged.
No matter how the generator is dried, the insulation resistance value should be recorded every half an hour and the record should be drawn into a figure.
Steps of insulation test
Disconnect all electronic components, such as AVR, electronic protection devices, etc. If a winding temperature detector (RTD) is installed, it should be grounded. And short the diode on the rotary rectifier. Please note if there are any components in the system that cause incorrect readings or may be damaged by test voltage. The insulation test shall be performed in accordance with the operation manual of the test instrument. Compare the measured insulation resistance values of all phases and phases,Phase to earth to the reference value of the above different life stages, and the minimum value should be greater than 1.0MΩ.
If it is confirmed by one or more methods that the insulation resistance is too low, the windings should be dried as follows.
How to evaluate the winding state?
The state of the winding can be evaluated by detecting the insulation resistance of phases and phases,Phase to earth. The winding insulation should be tested in one of the following cases: a. As part of a regular maintenance plan b. When the unit is not running for a long time. c. When the insulation resistance is suspected to be low, for example, the winding is wet or dirty. Extreme care should be taken when the insulation resistance is suspected to be low due to excessive moisture or dirt in the windings. The initial test of insulation resistance shall be carried out with a low voltage (500V) megger. If manual operation is used, the handle of the megger shall be slowly turned at the beginning to avoid the test full voltage being applied to the winding, and the duration shall be sufficient to judge the insulation condition of the winding. The megger full voltage test or other forms of high voltage test shall be carried out after the winding is dry or cleaned (if necessary).
How to extend the operating life of the bearing?
Bearing life is directly related to working conditions and the environment.
The vibration of the engine is too large or the bearing is subjected to lateral force due to the misalignment of the unit, which reduces the bearing life. If the vibration exceeds the specified value of BS5000-3 or lS08528-9, the bearing life will be reduced.
Long-term storage in a vibrating environment causes the generator to be forced to vibrate, resulting in the Brinell effect, the steel ball is deformed and dents are created on the raceway, leading to premature damage.
Very humid climates or humid environments can emulsify grease, which can cause corrosion and premature bearing damage.
We recommend that users use monitoring devices to check bearing conditions. The best way is to use the initial running value as a benchmark, and periodically check the bearing to understand its wear tendency. This makes it possible to plan for bearing replacement during unit or engine maintenance.
Most generators are similar in appearance, so are the technologies, workmanship and performance qualities the same?
In fact, for different generator, technologies and workmanship are different, and their performance and quality are also different.
Does the material used in the generator have a great impact on the performance and quality of the generator?
Big. For example, low-grade silicon steel sheets have large iron consumption and weak magnetic induction strength, which have a direct impact on performance indicators such as generator temperature rise.
Does the production workmanship of the generator have a great impact on the performance and quality of the generator?
Very big. For example, the accuracy of the angle of the stator slot is insufficient, which has a direct impact on the waveform distortion rate of the generator.
Does the generator have high requirements for equipment and tooling?
High. For example, The stator core lamination tire expansion,the combined tire expansion is worse than integrated tire expansion, and the quality of the stator core made by the integrated tire expansion is much better than the combined tire expansion
Will users feel that the quality of different generators is similar?
No. The problem is that the user has not carried out a comprehensive test, including full power test and various performance tests, so the quality between different generators cannot be distinguished.