A high-voltage motor refers to a motor with a rated voltage above 1000V. The voltages of 6000V and 10000V are often used. Due to the different power grids in foreign countries, there are also voltage levels of 3300V and 6600V. High-voltage motors are produced because the power of the motor is proportional to the product of voltage and current. Therefore, the power of low-voltage motors is increased to a certain extent (such as 300KW/380V). The current is limited by the allowable capacity of the wire. It is difficult to increase or the cost is too high. Need to increase the voltage to achieve high power output. The advantages of high-voltage motors are large power and strong impact resistance; the disadvantages are large inertia, difficult to start and brake.
Application:
The most widely used of various motors is AC asynchronous motors (also known as induction motors). It is easy to use, reliable in operation, low in price and firm in structure, but it has a low power factor and difficult speed regulation. Synchronous motors are commonly used in power machines with large capacity and low speed (see synchronous motors). The synchronous motor not only has a high power factor, but its speed has nothing to do with the size of the load, and only depends on the grid frequency. Work is more stable. DC motors are often used in occasions requiring wide-range speed regulation. But it has a commutator, complex structure, expensive, difficult to maintain, and not suitable for harsh environments. After the 1970s, with the development of power electronic technology, the speed regulation technology of AC motors has gradually matured, and the price of equipment has been decreasing, and it has begun to be applied. The maximum output mechanical power that the motor can bear under the specified working mode (continuous, short-time operation system, intermittent cycle operation system) without causing the motor to overheat is called its rated power, and pay attention to the regulations on the nameplate when using it. . When the motor is running, attention should be paid to match the characteristics of the load with the characteristics of the motor to avoid running or stalling. Electric motors can provide a wide range of power, from milliwatts to 10,000 kilowatts. The motor is very convenient to use and control. It has the capabilities of self-starting, acceleration, braking, reverse rotation, and holding, which can meet various operating requirements; the motor has a high working efficiency without smoke, odor, environmental pollution, and noise. Also smaller. Because of its series of advantages, it is widely used in industrial and agricultural production, transportation, national defense, commerce, household appliances, and medical electrical equipment. In general, the output power of the motor will vary with the speed when it is adjusted.
YRKK series high-voltage motors can be used to drive various machinery. Such as ventilators, compressors, water pumps, crushers, cutting machine tools and other equipment, and can be used as prime movers in coal mines, machinery industry, power plants and various industrial and mining enterprises.
In addition, we have other serious products. Such as, slip ring induction motors, wound rotor induction motors, slip ring motor, ac slip ring motor. If you want other models of products, you can contact our customer service.
Use classification of each motor series:
In addition, if you want other models of products, you can contact our customer service.
YRKK series 6.6kV (710-800) high-voltage three-phase asynchronous motors can be used to drive various machinery. Such as ventilators, compressors, water pumps, crushers, cutting machine tools and other equipment, and can be used as prime movers in coal mines, machinery industry, power plants and various industrial and mining enterprises.
YRKK series 11kV high-voltage motors can provide larger starting torque under a small starting current; the feeder capacity is not enough to start the squirrel cage rotor motor; the starting time is longer and the starting is more frequent; a small range of high speed is required. Such as dragging winches, rolling mills, wire drawing machines, etc.
6.6KV High Voltage Motors:
YRKK series 6.6kV (710-800) high-voltage three-phase asynchronous motors are linear rotor asynchronous motors. The protection class of the motor is IP44/IP54, and the cooling method is IC611. This series of motors has the advantages of high efficiency, energy saving, low noise, low vibration, light weight, reliable performance, and convenient installation and maintenance. The structure and installation type of this series of motors is IMB3. The rating is a continuous rating based on the continuous duty system (S1). The rated frequency of the motor is 50Hz and the rated voltage is 6kV. Other voltage levels or special requirements can be contacted with the user when ordering Negotiate together.
11KV High Voltage Motors:
YRKK series 11KV wound rotor three-phase asynchronous motors are products of my country in the 1980s, and their power levels and installation dimensions are in compliance with International Electrotechnical Commission (IEC) standards. This series of motors has the advantages of high efficiency, energy saving, low noise, low vibration, light weight, reliable performance, and convenient installation and maintenance. This series of motors adopt F-class insulation structure, and the bearing structure is designed in accordance with IP54. It is lubricated by grease and can add and drain oil without stopping the machine.
Speed regulation:
From the perspective of market conditions, high-voltage motor speed regulation technologies can be divided into the following types:
1. Fluid coupling
An impeller is added between the motor shaft and the load shaft to adjust the pressure of the liquid (usually oil) between the impellers to achieve the purpose of adjusting the load speed. This speed regulation method is essentially a slip power consumption method. Its main disadvantage is that as the speed drops, the efficiency becomes lower and lower, the motor needs to be disconnected from the load for installation, and the maintenance workload is large. Shaft seals, bearings and other parts are replaced, and the site is generally dirty, which means that the equipment is of low grade and is an obsolete technology.
Manufacturers who were more interested in speed control technology in the early days, either because there was no high-voltage speed control technology to choose from, or considering the cost factor, there are some applications for fluid couplings. Such as water pumps from water companies, boiler feed pumps and induced draft fans in power plants, and dust removal fans in steel mills. Nowadays, some old equipment has been gradually replaced by high voltage frequency conversion in the transformation.
2. High-low-high inverter
The frequency converter is a low-voltage frequency converter, which uses an input step-down transformer and an output step-up transformer to realize the interface with the high-voltage power grid and the motor. This was a transition technology when the high-voltage frequency conversion technology was immature.
Due to the low voltage of the low-voltage inverter, the current cannot rise without limit, which limits the capacity of this inverter. Due to the existence of the output transformer, the efficiency of the system is reduced and the area occupied is increased; in addition, the magnetic coupling capacity of the output transformer is weakened at low frequency, which weakens the load capacity of the inverter when it is started. The harmonics of the power grid are large. If 12-pulse rectification is used, the harmonics can be reduced, but it cannot meet the strict requirements for the harmonics; while the output transformer is boosting, the dv/dt generated by the inverter is also amplified, and filtering must be installed It can be suitable for ordinary motors, otherwise it will cause corona discharge and insulation damage. This situation can be avoided if a special variable frequency motor is used, but it is better to use a high-low type inverter.
3. High and low inverter
The frequency converter is a low-voltage frequency converter. A transformer is used on the input side to change the high voltage to low voltage, and the high voltage motor is replaced. A special low voltage motor is used. The voltage level of the motor is varied and there is no unified standard.
This approach uses low-voltage frequency converters with relatively small capacity and large harmonics on the grid side. 12-pulse rectification can be used to reduce harmonics, but it cannot meet the strict requirements for harmonics. When the inverter fails, the motor cannot be put into the power frequency grid to run, and there will be problems in the application in some occasions that cannot be stopped. In addition, the motor and cable must be replaced, which requires a relatively large amount of work.
4. Cascade speed control inverter
Part of the rotor energy of the asynchronous motor is fed back to the power grid, thereby changing the rotor slip to achieve speed regulation. This speed regulation method uses thyristor technology and requires the use of wound asynchronous motors. Today, almost all industrial sites use squirrel cage asynchronous motors. , It is very troublesome to replace the motor. The speed control range of this speed control mode is generally about 70%-95%, and the speed control range is narrow. Thyristor technology is likely to cause harmonic pollution to the grid; as the speed decreases, the power factor on the grid side also becomes lower, and measures need to be taken to compensate. Its advantage is that the capacity of the frequency conversion part is small, and the cost is slightly lower than other high-voltage AC frequency conversion speed regulation technologies.
There is a variation of this speed regulation method, that is, the internal feedback speed regulation system, which eliminates the need for the inverter part of the transformer, and uses the feedback winding directly in the stator winding. This approach requires the replacement of the motor. Other aspects of performance are related to the cascade regulation. Fast approach.
Protective device:
Motor differential protection devices are mainly used in large high-voltage motor power plants, chemical plants and other places. If a serious failure causes the motor to burn out, it will seriously affect the normal production and cause huge economic losses. Therefore, it must be fully protected. The existing integrated motor protection device is mainly for small and medium-sized motors, providing protection functions such as current quick-break, thermal overload inverse time overcurrent, two-stage definite negative sequence, zero sequence current, rotor stagnation, excessive starting time, and frequent starting. . As for the extra-large-capacity motors above 2000KW, they cannot meet the requirements of protection sensitivity and quick-action performance in case of internal failures. Therefore, this device is developed and combined with a comprehensive protection device to provide more reliable and sensitive protection measures for high-voltage motors. This device is designed as a three-phase longitudinal difference, because the 3KV, 6KV, and 10KV power grids where the extra-large capacity motors above 2000KW are located may be grids where the neutral point of the transformer is grounded by high resistance. The three-phase longitudinal differential protection can not only be used as the stator winding of the motor. The main protection for short-circuit between phases and lead wires, and can be used as the main protection for single-phase ground faults, acting on instantaneous tripping.
Nano insulating materials:
Since the 1980s and 1990s, the research on nano-dielectrics in the field of insulating material manufacturing and application has been very active. Some nanocomposites with excellent performance have been introduced in European and American countries in the early 1990s, such as corona resistant polyamide. Imine film, corona resistant enameled wire, nano composite cross-linked polyethylene high voltage cable, etc. These nanocomposite materials have outstanding performance in terms of corona resistance and partial discharge resistance, which are dozens or even hundreds of times higher than traditional materials. After they came out, they were quickly applied in the fields of variable frequency motors and high-voltage cables.
The use of nanoparticles to enhance the modification of main insulation materials is one of the important development trends for main insulation of high-voltage motors. Some foreign companies have completed wire rod tests on nanocomposite main insulation and have entered the prototype trial production stage, while related research in my country It has just started, and the manpower and material resources invested are still lacking. We should not be accustomed to imitating or introducing new foreign products after they come out. This will not be able to catch up with the advanced level of foreign countries, such as corona-resistant polyimide film, corona-resistant enameled wire paint and other products, we have imitated for more than ten years It is a typical example that it has not reached the level of foreign advanced company products. In addition to factors such as poor tooling and equipment, some key technologies are difficult to imitate, such as nano-dispersion technology and powder surface modification technology. Due to commercial and technical barriers and other reasons, it is expected that these key technologies will not be disclosed or transferred abroad in the short term. Only through independent research can we master the relevant core technologies and narrow the gap with foreign technologies.
The difference between high voltage motor and low voltage motor
1. The insulation materials of the coils are different. For low-voltage motors, the coils mainly use enameled wire or other simple insulation, such as composite paper. The insulation of high-voltage motors usually adopts a multilayer structure, such as powder mica tape, which has a more complex structure and a higher voltage resistance. high.
2. The difference in heat dissipation structure. Low-voltage motors mainly use coaxial fans for direct cooling. Most high-voltage motors have independent radiators. There are usually two types of fans, one set of internal circulation fans, one set of external circulation fans, and two sets The fans run at the same time, and heat exchange is performed on the radiator to discharge the heat outside the motor.
3. The bearing structure is different. Low-voltage motors usually have a set of bearings at the front and rear. For high-voltage motors, because of the heavy load, there are usually two sets of bearings at the shaft extension end. The number of bearings at the non-shaft extension end depends on the load. The motor will use sliding bearings.
High voltage motor and low voltage motor
Low-voltage motor refers to a motor with a rated voltage lower than 1000V, and a high-voltage motor with a voltage higher than or equal to 1000V.
The rated voltage is different, the starting and working current are different, the higher the voltage, the smaller the current; the insulation and withstand voltage of the motor are also different, the wires of the motor windings are also the same, the same power motor, the high voltage motor wire is lower than the low voltage There are fewer cables, and the cables used are different.
Analysis of Bearing Failure of High Voltage Motor
Most of the bearings are broken due to many reasons, beyond the originally estimated load, ineffective sealing, too small bearing clearance caused by tight fit, etc. Any of these factors has its own special type of damage and will leave special damage marks.
Inspect the damaged bearings, in most cases, the possible causes can be found. Generally speaking, one third of bearing damages are caused by fatigue damage, the other third are caused by poor lubrication, and the other three points. One is due to contamination entering the bearing or improper installation and treatment.
According to analysis, most high-voltage motors are end cover sliding bearing structure and end cover rolling bearing structure. After summarizing and analyzing the maintenance experience of various high-voltage motors, we believe that there are the following problems: End cover sliding bearing type: most of these motors have large axial series movement of the rotor, heating of the bearing bush and oil leakage. It causes corrosion to the stator coil of the motor, and causes excessive oil and dust inside the motor, resulting in poor ventilation and damage to the motor due to excessive temperature. Sliding bearings are also much more complicated than rolling bearings.
Box-type high voltage motor: This motor is a new type of motor produced in my country in recent years, and its performance and appearance are superior to JS series motors. However, the motors produced by some manufacturers have some deficiencies in the design of the bearings, resulting in more bearing failures during the operation of the motors. The structure of these motors is equipped with an oil baffle with a small clearance from the bearing on the outside of the bearing, so that the grease inside the bearing can be kept sufficient, but this structure has the following disadvantages:
Due to the existence of the bearing oil baffle plate, the motor cannot be inspected even if the bearing cover is opened during minor repairs. However, during the overhaul of the motor, the bearing cannot be cleaned and inspected without removing the oil baffle plate. Only replacement is required, which causes unnecessary waste. It is not conducive to the heat dissipation of the bearing and the circulation of lubricating grease, so that the temperature of the bearing increases during operation, and the performance of the lubricating grease decreases, which in turn causes a vicious cycle of temperature rise again, which damages the bearing. Due to the need to disassemble the oil baffle and replace the bearing during multiple maintenance, the inner hole of the oil baffle and the shaft are loosened, and the oil baffle is detached from the shaft during operation, causing failure.
Bearing type: The bearings on the negative side of most motors in my country are cylindrical roller bearings, and the air side is a centripetal thrust ball bearing. During the operation of the motor, the length of the rotor is adjusted by the negative side. If the coupling of the motor and the machine is an elastic coupling, it will not have a big impact on the motor and the machine. If it is a rigid coupling, the motor or machine will vibrate and even cause damage to the bearing.
Double-bearing motors: Some high-voltage motors currently produced in our country adopt a double-bearing structure on the load side. Although this increases the radial load-bearing capacity of the load side, it also brings difficulty to the maintenance. When the motor is overhauled, the bearing cannot be cleaned and inspected and must be replaced, otherwise the quality of the repair cannot be guaranteed, which causes an increase in the cost of the repair. In motors with this structure, most bearings have a relatively high temperature during operation, which reduces the service life of the bearings and damages them.
Bearing selection problem: According to our analysis and calculation of motor bearings, the failure of the bearing has a great relationship with the selection of the bearing. From the comparison of my country's motors with imported motors, the load-side bearings of domestic high-voltage motors generally use medium-sized roller bearings. The radial load capacity of the bearing greatly exceeds the calculated value, but the allowable speed differs from the actual speed of the motor very little, causing the bearing to fail to reach the rated service life. The bearing on the load side of the imported medium-sized motor generally uses a larger light ball bearing, while the no-load side uses a light roller bearing smaller than the load side. This not only ensures the bearing capacity, but also the allowable speed of the bearing greatly exceeds The actual speed of the motor can be reached or exceed the service life of the bearing.
