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General-purpose inverters selection, installation, measurement and wiring specifications
1、Inverter Selection The correct choice of frequency converter for controlling the normal operation of the system is very critical. Select frequency converter must be fully aware of inverter-driven load characteristics. In practice, people are frequently divided into three types of production machinery? Charge constant torque load, constant power load and fans, water pump load。
Constant torque load:
TL the load torque has nothing to do with the speed n and any constant speed under the total TL or basic constant. For example, conveyors, mixers, extrusion machines and other friction type loads, as well as crane, hoist, etc. are all potential energy load constant torque load。
Constant torque converter drag the nature of load, low speed torque should be large enough and has enough overload. If you need to run at low speed under steady consideration should be given the standard induction motor cooling ability to avoid excessive temperature rise of the motor。
Constant Power Load:
Machine tool spindle and the rolling mill, paper machine, plastic film production line in the take-up machine, open-book machines required torque and speed is inversely proportional to the general, and this is the so-called constant power load. Constant-power nature of the load should be on a certain speed range for the purposes of. When the speed is very low, limited by the mechanical strength, TL can not be infinitely increased, in the low speed into the nature of constant torque. Constant power load, constant torque region and the choice of the program areas to drive a great impact on。Motor at constant flux speed, the maximum allowable output torque constant, are constant torque speed; in a weak magnetic speed, the maximum allowable output torque and speed is inversely proportional to speed are constant power. If the motor constant torque and constant power speed range and load range of constant torque and constant power is consistent, that is the so-called "match" circumstances, the motor capacity and the capacity of both the minimum inverter。
Fan, pump load:
In a variety of fans, pumps, oil pumps in the rotation with the impeller, air or liquid at a certain speed range, the resistance produced by roughly proportional to the speed n-th power of 2. As the speed decreases, the speed by reducing the speed of the 2-th power. This loads the required power and speed is proportional to the 3-th power. When the required air volume and flow are reduced, the use of inverter to adjust the way through the speed of air flow, flow, can greatly save energy。As the power required at high speed with the speed of growth too fast, and speed is proportional to the cube, it should not generally fans, pumps and load-frequency ultra-running。
wan Long company can provide different types of converter, users can process according to their own requirements and the use of the actual occasion choose different types of converters. In selecting inverter due to note the following considerations:
1. Choice depending on the load characteristics of inverter, such as the load is constant torque load must select the general-purpose inverter; such as the load is fan, pump load should choose the type of wind pump inverter。
2. Select frequency converter should be the actual motor current value as the converter of choice based on the motor rated power only as a reference. It should also be fully consider the output of inverter contains high frequency harmonics will cause the motor power factor and efficiency will be worse. Thus, inverter to the motor power supply frequency of power supply and employment compared to the motor current is increased by 10% while the temperature increase of 20% or so. Therefore, in selecting motor and inverter should be taken into account the situation, the appropriate left margin, in order to prevent excessive temperature rise, affecting the life of motor。
3. Inverter to long cable runs, this time should take measures to curb long cable-to-ground impact of coupling capacitance to avoid the inverter is not enough to contribute. Therefore, to enlarge a file converter should be selected or installed at the output of the inverter output reactor。
4. When the inverter is used to control several motors in parallel, we must consider the frequency converter to the motor cable length of the sum of the inverter within the permissible range. If more than the specified value, it is necessary to enlarge a file or two stalls to choose the frequency converter. Also in this case, the inverter control mode only for the V / F control method, and the inverter can not protect the motor over-current, overload, this time need to add each motor protection fuses to achieve the。
5. For some specific applications, such as high ambient temperature, high switching frequency, high-altitude and so on, at this time will cause lower capacity inverter, inverter required to enlarge a file selection。
6. The use of high-speed motor inverter control, due to high-speed motor reactance is small, high-order harmonic has also increased the output current value. Therefore, the choice for high-speed motor inverter should be slightly larger than the average number of motor inverter。
7. Inverter for variable-pole motors, they should give full attention to the selection capacity of the inverter so that the maximum rated current of the inverter rated output current of the following. In addition, the operation of the very few conversions, they should first stop motors work, otherwise it will create motor idling, the poor will cause inverter damage。
8. Driven explosion-proof motor, the inverter is not explosion-proof structure, should be set up in dangerous places outside the inverter。
9. The use of inverter-driven gear motors, the use of gear by rotating part of the lubrication constraints. Oil lubrication, there is no limit in the low range; in more than the rated speed, high-speed range of the above, there may occur the risk of running out of oil. Therefore, do not exceed the maximum speed allowed values。
10.Wound rotor induction motor inverter drive, the most use of existing electric motors.
Winding motor, compared with the ordinary squirrel-cage motors, winding motor winding impedance. Therefore, prone to the ripple current is caused due to over-current trip phenomenon, we should choose the size slightly larger than the usual inverter. General winding motors are used for the flywheel torque GD2 larger occasions, the set should pay more attention to acceleration and deceleration time。
11.Inverter-driven synchronous motor when the power supply, compared with the frequency and reduce the output capacity of 10% to 20%, inverter continuous output current greater than the synchronous motor rated current and the synchronous pull-in current-unit value of the product。
12.For the compressor, vibration machine torque fluctuations in a large hydraulic pump load and peak load conditions such as there is, if the motor rated current or power converter, then the value of choice, it may occur due to peak current so that the phenomenon of over-current protection action . Therefore, we should understand the frequency operation, select the maximum current greater than its rated output current of the inverter. Inverter-driven submersible pump motors, because of submersible pump motors rated current of the motor rated current than the usual big, so I chose converter, its rated current greater than the rated current of submersible pump motors。
13.When the transducer control blower, because of their large starting current, so I chose when the Inverter must pay attention to the capacity of inverter is large enough to。
14.Select frequency converter, we must pay attention to whether its protection level to match the scene conditions. Otherwise, the scene of dust, water vapor will affect the long-term operation inverter。
15.Not apply to single-phase motor inverter drive。
2、Inverter installation and wiring specifications:
Installation Environment:
Inverter can be stable in order to work, you must ensure that the inverter’s operating environment to allow the environment to meet their required。
Installation place:
1、Electric wet steam room should be small, no flooding
2、Non-explosive, incendiary or corrosive gases and liquids, dust less
3、Maintenance checks easily
4、Should be equipped with vents or ventilation device to emit the heat generated by inverter
3、Conditions of Use:
1、Multi-inverter operating temperature is: -10 ~ 0 ~ 40 or 50, should pay attention to the ventilation of inverter enclosure。
2、Inverter humidity around 90% or less. The surrounding humidity is too high, there are electrical lasting bonds and metal parts to reduce corrosion problems. If you install the places affected by the restrictions, inverter installed in high humidity forced to place the inverter enclosure should be sealed structure. To prevent the inverter stops condensation, and sometimes need to increase convection heater installation。
3、Inverter should not be corrosive surroundings, explosive or incendiary gases and dust and oil mist. If the installation of converters around the explosive and combustion gases, due to frequency converter is easy to produce sparks inside the relays and contactors, so sometimes cause fires or explosions. Corrosive gas is corrosive to metal parts, affecting the long-running inverter. If there is dust and mist around the inverter, these gases in the converter inside the attachment, accumulation will lead to lasting bonds reduced; for forced air cooling of the inverter, due to filter blockage will cause the abnormal rise in the temperature converter, causing inverter can not be stable operation。
4、Vibration-resistance of the inverter models to be rather different than inverters to allow vibration value, will result in some loosening of fastening components, as well as relays and contactors, etc. movable part of the device malfunction, often leads to frequency converter is unable to stabilize run. For machine tools, ships, etc. in advance to foresee the vibration of occasions, should consider the problem of vibration transducer。
5、Multi-frequency converter provides elevation below 1000m. Under the high-pressure elevation would be easy to create lasting bonds destroyed. In addition the cooling effect of the high elevation also decreased, must pay attention to temperature rise。
4、Inverter Wiring:
In a variety of plant and equipment using frequency control when the power supply side of the inverter and motor side will have a harmonic disturbance of the surrounding power grid and the inverter and other electrical equipment to produce EMC interference. Also in order to ensure long-term reliable operation of inverter, inverter wiring is very important to。
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