In the past, most of the White-Box tablet manufacturers in mainland China chose Zhuhai's Quanzhi and Fuzhou's Ruixin microprocessors. Because they are white, they are very sensitive to price. Now more and more manufacturers have already Turn to MediaTek solutions, especially quad-core processors such as MediaTek MT8125 and MT8135.
In addition to white-brand manufacturers, MediaTek's tablet chip solutions have also been adopted by a number of "big manufacturers", including Acer, Asus, Liaison and Xiaomi. The prices of tablets based on MediaTek's solutions are between $99 and $199. Snatched the market for white-label tablet manufacturers. The white-plated tablet makers only turned to MediaTek, hoping to launch products with the same performance but lower prices to regain the market.
MT8125 quad-core processor introduction
MT8125 is a MTK quad-core processor specially designed for flat panel. This processor adopts Cortex-A7 architecture, clocked at 1.3GHz and integrates PowerVR Series5XT graphics processor. In theory, it supports up to 1080P HD screen.
The highest frequency is 1.5GHz, including four Cortex-A7 cores. The built-in GPU is PowerVR Series 5XT (up to 1920&TImes; 1200 resolution), and supports up to 13 megapixel camera and 1080 video recording. In addition, MediaTek's MT8125 quad-core processor also supports 3G HSPA+, 2G EDGE network, integrated Wi-Fi, Bluetooth 4.0, GPS and FM radio function modules.
How about MT8125 quad-core processor--analysis comparison between MT8125 and MT8389
After MediaTek released the MT6589 quad-core SoC, quad-core mobile phones and tablets have sprung up, the MT6589 SoC for quad-core mobile phones, and the MT8389/MT8125 SoC for quad-core tablets. What is the relationship between the three, and their differences Where is it?
MT6589 brings the big screen quad-core into the thousand-yuan era, and its reputation is very high. The thousand-core quad-core mobile phones on the market are almost all MT6589 SoC, A7 architecture, and the power consumption has a good performance and has been recognized by the market. Then, in the field of flat panels, domestic solutions, such as Ruixinwei, Actions, and Crystal Morning in the United States.
How can MediaTek lose the big piece of flat tablet, quoted Dai Zi’s words: "In essence, whether it is MT8125 or MT8389, they are a branch of MT6589, a clone branch, and it is clear that it is a high-cost version of MT6589 ( This will be discussed in detail later, if you think of them as the same CPU is also possible. Before writing this text, I would like to find out the difference between MT8125 and MT8389, but unfortunately rummaged through the entire technical documentation, but Nothing to gain, just like playing with everyone to find 茬, looking for a long time can not find a difference. It seems that the only difference between MT8125 and MT8389 is only the "name" is different, and the difference between MT8125 and MT6589 is that the energy consumption is different." , MediaTek made a slight change, the tablet quad-core processor came out.
So what is the difference between MT6589, MT8125 and MT8389?
From the official website of MediaTek, MT6589 belongs to the smartphone, and MT8125 and MT8389 are indeed the same series. The official website of MediaTek directly merges the introduction of the two.
Analytical comparison of MT8125 and MTK6592
Processor MediaTek MT8125 core number quad-core processor speed 1.2GHz display chip SGX-544 is mainly used for flat panel, security free running around 13000
Processor MediaTek MT6592 core number eight core processor speed 2.048GHz display chip Mail 400 series security free running around 30,000
The insulation breakdown accident often occurred in generator. It includes interphases short circuit, inter-turn short circuit and ground fault.
The interphase short circuit: the generator windings ends will be greatly impacted by electric power and may make the coil end deformed under two-phase or three-phase short circuit and differential protection tripping happening.
Inter-turn short circuit: Generator outlet blasting, if it continues a long time, the stator copper wire will be melted. When no-load run, the generator three-phase voltage will be imbalance.
Ground fault: Generator breakdown location is in the linear portion or notch position and stator ground protection act. The insulation resistance value between stator ground and ground is zero or minimum.
The fundamental reason of generator insulation breakdown is that the stator coil insulation is weak or there is a corona etching in notch in run time. The treatment method is to find the point of breakdown and reworked and reinforced insulation. At the same time, eliminating the corona etching in a maximum extent is important.
III. A large noise or vibration with generator
The reasons of a large noise or vibration with generator are:
1. Foundation bolts loose, or STG subsidence. Treatment: fastening bolts. Recalibration concentricity.
2. Generator rotor and steam turbine shaft are misalignment. Treatment: calibration concentricity.
3. Bearing wall worn or damaged under short oil. Treatment: repaired bearing or replace a new bearing with same model.
4. There is a friction between the stator and rotor. Treatment: find the friction location and reason, and then eliminate it.
5. Fan or other fasteners loose. Treatment: Tighten fan and fasteners.
6. Rotor coil partial short circuit, two points grounding or wiring errors. Treatment: please inspect the insulation of slip ring and the rotor coil to the ground. Or connect to the DC power source and check the voltage drop of each coil, winding direction and wiring method. So we can identify the cause of the malfunction and eliminate them.
7. Brush is too hard, or the pressure is too large. Treatment: adjust the pressure or replace the same type of brush.
8. Three-phase current are severe asymmetry. Treatment: please investigate that the three-phase current imbalance is in the allowable range or not. If it is not in the allowable range, please adjust three-phase load or reduce the load.
9. Stator winding short circuit or ground. Treatment: Find out the fault and repair it.
10. External fault or lightning strike. Treatment: if the vibration time is too long, please stop the STG and inspect.
Typical
cases:
This is a 15 MW generator from a Shandong customer. The vibration of generator is reached to 0.12mm in running. After inspection the generator, we found that rotor dynamic AC impedance upheaval 12% in 2400-2700 and the dynamic inter-turn short circuit is serious. It destroys the balance of the magnetic field and causes the electromagnetic force uneven of generator rotor. After removal of the rotor retaining ring and treatment the rotor inter-turns, we start the STG. The vibration is about 0.01mm.
IV. The temperature of a generator is too high.
Generally the temperature of a generator will be in the allowable value, if the generator running normally and the current, voltage, frequency, power, excitation current and power factor are all within the allowable fluctuation range. If a generator stator, core and other parts temperature are too high, please consider the following cases:
1. Generator overload operation and exceed the allowable time. Treatment: Please reduce the generator load to the rated load or under rated load as soon as possible.
2. Three-phase current are serious imbalance. Treatment: please find out the reason of imbalance. If it is the voltage causing, please check if it is the generator inter-turn short circuit. If it is load causing, please adjust the load and make it balance.
3. The ventilation cooling system of generator is poor. For example, the temperature is too high, the air duct or exhaust duct are blocked, the coil and its ends are serious fouling. Treatment: please reduce the load suitability, improve ventilation, and remove fouling.
4. The stator winding portion short circuit or ground. Treatment: Find out the short circuit or ground point and repair them, and then eliminate short circuit or ground risks.
5. Insulation of the stator core may be partially damaged and short circuit, so there is a vortex and overheat. Treatment: please reduce the load suitability. If the generator reduces its efficiency obviously, please repair the generator stator core.
6. The bearing is short of lubricating oil. The oil number is wrong. The oil quality is bad. The bearing is installed with a wrong way or the bearing is damaged. Treatment: please find out the reason and then replace the oil or clean, adjust or replace bearing.
V. Generator rotor ground
Symptom: Generator grounding one point or two points grounding light plate light.
Fault Analysis: Generator rotor winding insulation damage, coil deformity and severe dust and greasy attached in the ends seriously are all leading to the grounding of the generator rotor windings. When the generator rotor winding grounding in one point, there is electrical current pass as the ground does not constitute an electrical circuit.
However, after one point grounded, it is easy of leading another grounding point. If any part in excitation circuit ground, it can form ground fault of two or more points ground. It is very dangerous.
After the failure, the rotor windings are short-circuited. Because of the small winding DC resistance, the excitation current will increase. So the magnetic field of generator is out of balance, and main magnetic flux reduces largely. So the STG will vibrant strongly. Meanwhile the power factor of the generator will be increased significantly and get into leading phase running (absorption of reactive power from the grid).
The stator field becomes in the frond and the rotor field becomes in the back. It will make the stator current increases. If the watcher notice that there is no excitation varying but the excitation current and stator current suddenly increases, and the excitation voltage and AC voltage are all suddenly drop, and power factor meter indicates increasing or leading phase, it means the generator rotor grounded or inter-turn short circuited. You should shut down the STG and blow-out magnetic. Please inspect the excitation system and rotor windings, and find out the short circuit point and treat it.
VI. Excitation upgrading and generator test
Excitation system upgrading, brushless exciter changes into the SCR excitation and make the generator maintenance easily. And it removes the disadvantage of brushless excitation dynamic adjustment slowly. The generator test includes stator insulation resistance test, the absorption ratio test, the iron loss test, leak test, AC and DC voltage withstand test, the rotor high speed balancing and overspeed test, dynamic and static AC impedance test, the generator no-load test, short circuit test, temperature rise test, residual pressure measurement, axis voltage measurement.
Generator Care,Steam Turbine Generator Care,Msw Power Generation,Combined Cycle Generating Unit
Shandong Qingneng Power Co., Ltd. , https://www.steamturbine.be