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Analysis of Common Faults of Shanghai Gasoline Generator
With the widespread use of generators in various industries, many customers are at a loss when they encounter machine failures. Today, Hansa Power shares with you the analysis of the common fault conditions of Shanghai gasoline generators:
1. Shanghai Gasoline Generator and Rectifier Power Equipment 1.1 Yamaha EU-5500DE Generator Set Related Data Parameter Generator: Rated voltage (3 phase) 380/220V; Frequency: 50Hz; Maximum output 5.5kVA; Rated output 5.0kVA; Rated current 7.2A. Engine: 4-stroke air-cooled OHV; displacement 357CC, maximum power 12PS/4000r/min, ignition method: TCI.
1.2 High-frequency switching power supply Taizhou Mobile Branch mainly uses two manufacturers' high-frequency switching power supply systems, which are: (1) Hangzhou Zhongheng System Co., Ltd.: RPS17-450 system and E2733 module. (2) Shanghai Zhongda Dentsu: DUM94A-48/50 system and ESR3000 module.
2. Abnormal phenomenon when supplying power to Zhongheng E2733 module, and the solution 2.1 Abnormal phenomenon when supplying power to Zhongheng Power Supply System When the generator is used to supply power to the medium-constant power supply (E2733), the medium-constant power supply cannot be started, or cannot In normal operation, the module is in a state of start-stop-restart-stop again.
2.2, reason analysis The high frequency switch power is mainly made up of the input filter circuit, power factor correction circuit, DC-DC converter circuit and output filter and other departments, as shown.
After the single 220V AC power supply is connected to the rectifier module, it enters the EMI filter through AC circuit breakers, fuses, and other protection components. Its function is to prevent the rectifier module from being damaged by the surge voltage in the power supply and to effectively reduce differential mode and common mode noise. To eliminate incoming high frequency noise from the power supply and prevent the module's noise from feeding back to the power line. After the single AC power is rectified into DC by a bridge rectifier and then through an active power factor correction line (PFC), the high power factor (PF>0.99) and low distortion factor (THD>5%) are required to generate a 400V The DC voltage is supplied to the DC-DC converter. The 400V DC voltage generates an uninterrupted output voltage through the DC-to-DC converter. This sector uses a full-bridge series resonant zero-current switching technique to switch the DC 400V voltage to an AC sinewave with a switching frequency of 100kHz. Then through the high-frequency transformer step-down to an appropriate amplitude AC pulse.
The secondary side of the AC sine wave through the rectifier diode and the output filter circuit, and then fed back through the DC controller can get uninterrupted DC output, this output in the output before the rectifier module filter circuit common mode noise, the desired DC power supply. After analyzing the generator and power system circuit, the E2733 module was developed and produced in New Zealand. The quality of the AC power supply is relatively high. At the same time, the startup power of the module needs to reach about 5kW, but the maximum power required after the module is started is about For 3kW (calculated with a single module maximum output current of 50A, the efficiency of the module is approximately 90%). There is a situation where the startup power demand is large and the operating power demand is normal.
The output waveform of the Shanghai gasoline generator provided by our company: When the output is high power (or full load output, such as 5kW), the waveform distortion is severe, and the harmonics are more; when the output power is normal (70% Below), the output waveform of the generator is better, and the quality of the AC power is higher. The maximum output power of this type of generator is about 5.5kVA. When the module is powered on, because of the large power demand, the generator output waveform is instantaneously distorted, the quality of the AC power is reduced, and the rectifier's harmonic protection detection circuit starts the protection function. , Issue a module shutdown command. After the module is shut down, the output power of the oil generator is reduced, and the waveform resumes normal, so that the module is restarted. After startup, the waveform of the oil generator is distorted again, and the protection circuit operates again, and then the module is shut down. The phenomenon exhibited is that the rectifier module is in a vicious cycle of start-up protection-stop-restart-reprotection shutdown.
Through the above analysis, we carefully researched and analyzed the internal circuit diagram of Zhongheng Power Supply and the harmonic protection mechanism of the module. In the “AC Input Filtering Department†of the module, there is a harmonic detection protection circuit. As long as this protection circuit is disconnected, it can prevent When the module is powered on, the required output power is high and the output waveform of the oil generator is distorted instantaneously, causing the harmonic protection circuit to work and causing the protection shutdown.
For the oil turbine, after the module is started, the required power (about 3 kW) of the single module at full load is within the power range of the normal waveform output of the oil generator. Disconnecting this protection circuit will not have a major negative impact on the normal operation of the system. At the same time, according to the circuit analysis, after this protection circuit is interrupted, there will be no primary protection measure for the rectifier module: that is, before the removal, the module will be protected when the single-phase voltage reaches 270V or the input power quality is poor. After removal, the module will perform secondary protection at the input voltage up to 320V (high voltage shutdown), and the module will be reduced by one level of protection. Therefore, before the module is turned on, measure the input power supply voltage to ensure that the operating voltage is normal.
2.3. Solution The simplest method to remove the harmonic protection circuit of the Zhongheng Power Module is to disconnect the output of the harmonic circuit. The resistance of the R148 in the circuit is the output channel of the control signal.
(1) Open the panel of Zhongheng Power Module E2733: Remove the three Hexagon Socket Screws on the right side of the front panel of the module, remove the 11 self-tapping screws on the right side board of the module, and open the right side board; (2) Find the main One R148 resistor (harmonic detection protection circuit) in the upper left corner of the control board; (3) Disconnect the R148 resistor; (4) Reinstall the right side board of the module.
2.4 Test records and trials Test date: March 26, 2005. Test Rectifier Rack: Model No. RPS17-450.Serial No127226. Install four modified E2733s on the three-phase power supply of the rectifier, two phases of the B phase. When the generator is unloaded, the output voltage is A-phase 233V; B-phase 233V; C-phase 233V, neutral to ground voltage is about 0V. After loading the constant power module, the voltage of each phase is loaded. After testing, it was found that the modified Zhongheng power supply module can be powered by the Yamaha EF5500TE generator. And in single or multiple items, the module and generator can work normally. At present, our company uses the modified E2733 module to supply power from the oil machine. It has been running for nearly 300 hours and no abnormality or module damage has occurred.
3. Abnormal phenomena, causes and solutions for power supply to high-frequency switching power supply 3.1 Abnormal phenomena when power is supplied to the power supply system of Yamada YAMAHA power generation performance is normally started Shanghai Zhongda MCS series is loaded with a constant power supply module after the phase of each voltage condition Switching power supply , Module, but in the process of using the gasoline engine, found some problems, mainly include: (1) After the city stopped, the gasoline engine started to supply power, Zhongda switch power supply panel display voltage rises quickly, causing over-voltage alarm, In addition, We also found that the actual voltage (RMS) of the gasoline engine was found to be too high, but it was inconsistent with the panel display voltage. (2) With the increase in the load (increase in the rectifier module), the voltage is also increased, and the output voltage of the gasoline engine is not disorderly.
3.2 Test records and descriptions Test location: Taigao Road Base Station, switching power supply is Zhongda ES3000 series, with 3 50A modules, the actual load is about 10-20A, and the battery capacity is 300Ah×2. The experimental results are as shown. When the inductive load such as the exhaust fan and fluorescent lamp is turned on while the rectifier module is turned on, the voltage waveform becomes better, the power factor is improved, the peak voltage is greatly reduced, and the voltage displayed on the panel is also decreased. When tested with a purely resistive load, the performance of gasoline is stable within its rated power range, and the output voltage and frequency are all within specifications.
3.3, test conclusion
(1) Following the increase in the capacitive load of the rectifier module, the output voltage of the gasoline generator also increases; the voltage waveform is significantly degraded, and the peak voltage rises significantly. When the capacitive load of the rectifier module is further increased (within the rated power range), the output voltage of the gasoline generator will not be disorderly, and the gas generator will vibrate. (2) The voltage displayed on the panel of the Zhongda switching power supply is through sampling. Calculate the peak voltage: U=peak voltage
×0.707, its value changes along with the change of peak voltage, so when the voltage waveform becomes bad, the display panel generates AC input high voltage alarm; (3) Gasoline generator output voltage and other indicators, load type and load size Closely related.
3.4. Reason analysis
(1) Because the power of Shanghai gasoline generators is relatively small, we generally only use 5-6kW. When the capacitive load of the rectifier module is greater than 70% of the steam quantity, the higher harmonic current generated by the rectifier flows through the gasoline generator. Stator winding, the voltage waveform of the gasoline generator will produce a severe distortion, a substantial increase in the peak voltage. In this case, if you work long hours, it will cause two adverse effects, causing gasoline generators can not run indiscriminately and mechanical vibration. Harmonic currents cause the motor to overheat and accelerate the insulation aging of the motor, which is not only harmful to the gasoline generator, but also affects the unsteady operation of other equipments of the power system, that is, the oscillation problems that are currently encountered.
(2) Synchronous generator external characteristic curve It can be seen that the output voltage of the gasoline generator is closely related to the load type and load size. In capacitive loads, the output voltage increases with the increase of the current; when a resistive load is applied, the increase of the output voltage with the current does not substantially change; when the load is inductive, the output voltage decreases with the increase of the current. In summary, following the increase of the capacitive load of the rectifier module, the output voltage of the gasoline generator also increases.
3.5. Solution:
(1) When the gasoline engine is powered, try to open some inductive loads such as fans, fluorescent lamps, etc.; (2) When using a gasoline engine to supply power, there is a limit to the size of the load. For capacitive loads, if you work for a long time, it is better not to take the load. More than 70% of the rated power of the gasoline engine; (3) In the actual use, for the load current of the general base station is relatively small (50A or less), we have demarcated only one module is sufficient (after a long time power outage, the general work 55A current limiting state).
Reminder: In the current situation of the nationwide power shortage, Shanghai's small gasoline generators have played a major role in the emergency power supply system for mobile base stations with their portability, but the small gasoline generators have their own shortcomings: low power. The low power supply quality caused some inconsistencies in the power supply to high-frequency switching power supplies. As long as we can analyze the causes and find solutions, small gasoline power stations can still fully display their resistance to power shortages. The effect is to ensure that our mobile communication base station will never go offline and the mobile communication network will always be unblocked.