Phone: (0) 13805838073
Address: No. 297 Huiyuan Road, Economic Development Zone, Fenghua
Phone: (0) 13805838073
Address: No. 297 Huiyuan Road, Economic Development Zone, Fenghua
The inverter is the use of power semiconductor devices will be the role of the on-off frequency to another frequency power conversion power control device. We now use the drive mainly uses AC - DC - AC mode (VVVF inverter or vector control frequency), the first frequency AC power through a rectifier to convert the DC power into DC power and then converts the frequency and voltage can be controlled AC power supply to the motor. Inverter circuit generally consists of rectified DC link inverter and control four parts. Three-phase bridge rectifier is not controlled rectifier, inverter part of a three-phase IGBT inverter bridge, and the output of the PWM waveform, intermediate DC link for the filter, the DC energy storage and buffering reactive power.
To determine when the drive following selection:
1) The purpose of use of frequency; constant voltage control or constant current control.
Load Type 2) inverter; if vane pump or positive displacement pump, etc., with particular attention load performance curves, performance curves determined ways when applied.
3) matching the inverter and the load;
Inverter rated voltage and rated load voltage matches; I. voltage match.
. II current matching; ordinary centrifugal pump, rated current of the inverter and the motor rated current match. For special load such as deep water pumps and other electrical performance parameters you need to refer to in order to determine the maximum current drive current and overload.
. III torque to match; in this case, there is constant torque load or deceleration device might occur.
4) When using high-speed inverter-driven motor, since the electrical resistance of small high-speed motor, high harmonics increase the output current value increases. Therefore, selection for high-speed motor drive, its capacity to be slightly larger than an ordinary motor selection.
5) If you want to drive long cable runs, this time to take measures to suppress the influence of long cable coupling capacitance to ground, to avoid the lack of inverter output, so in this case, the drive you want to enlarge the capacity of a file or drive the output of the output of the reactor installation.
6) For some special applications, such as high temperature, high altitude, at this time will cause derating of the inverter, the inverter capacity should enlarge a block.
Inverter control schematic design:
1) First make sure the installation environment of the inverter;
I. operating temperature. Electronic components inside the drive is powerful, highly susceptible to operating temperature, the general requirements for product 0 ~ 55 ℃, but in order to ensure safety, reliability, should be used to consider the leeway, the best control below 40 ℃ . In the control box, the drive should be installed in the upper box, and strictly comply with the product specification, installation requirements, and definitely not easy to heat the heating element or elements close to the bottom of the installation of the drive.
II. Ambient temperature. Temperature is too high and the temperature change is large, prone to condensation inside the drive, the insulation performance will be greatly reduced, and may even lead to a short circuit accident. When necessary, the desiccant must be increased and the heater in the tank. During water treatment, generally heavier than water vapor, if the temperature changes, then the problem would be more prominent.
III. Corrosive gases. Environment if corrosive gas concentration, not only will corrode components leads, printed circuit boards, but also accelerate the aging of plastic components, reducing insulation performance.
IV. Vibration and shock. When equipped with inverter control cabinet subject to mechanical vibration and shock, can cause poor electrical contact. Huaian thermoelectric on such a problem. Then in addition to improving the mechanical strength of the control cabinet, away from sources of vibration and shock sources, we must also use the seismic rubber pad fixed outside the control cabinet and the like within the electromagnetic switch vibration components. After the device running for some time, and should be inspected and maintained.
V. electromagnetic interference. Drive at work due to the rectifier and inverter, generated around a lot of electromagnetic interference, these high-frequency electromagnetic waves in the vicinity of the instrument, the instrument has a certain degree of interference. Therefore, the cabinet instrumentation and electronic systems, should use a metal shell, shielding against interference inverter instrument. All components should be grounded wiring, in addition, all electrical components, equipment and instrumentation should be used between the shielded control cable, and the shield should be grounded. Electromagnetic interference if not handled properly, tend to make the whole system does not work, leading to the control unit malfunction or damage.
2) to determine the distance between the inverter and the motor cables and wiring methods;
Distance I. inverter and the motor should be as short as possible. This reduces the cable capacitance to ground, reducing the emission source of interference.
II. Control cables use shielded cables, power cables use shielded cable or conduit all with shields from the drive to the motor.
III. The motor cable should be independent of the other cable routing, the minimum distance of 500mm. While avoiding long-distance motor cables and other cables parallel lines, so as to reduce the inverter output voltage generated by rapid changes in electromagnetic interference. If the control and power cables cross, as far as possible so that they intersect at 90-degree angle. And drive-related analog signal line and the main line traces back to separate, even in the control cabinet also true.
IV. And related analog converter best selection of shielded twisted pair wire, power cables use shielded three-core cable (its size bigger than normal motor cable gear) or to comply with the inverter user manual.
3) inverter control schematic;
I. main loop: the role of the reactor is to prevent high harmonics generated by the drive back through the power of the input circuit to the grid in order to affect other powered devices, according to the capacity of the size of the inverter needs to decide whether to increase the reactor; filter is installed at the output of the inverter, reducing the higher harmonics of the inverter output when the motor drive to the far distance, you should install the filter. Although the drive itself has various protection functions, but lack of protection was not perfect, has played in the main circuit breaker overload, lack of equal protection, according to the capacity of the inverter selection selection. You can use the drive to replace the thermal overload relay.
. II control loop: a power frequency inverter manual switch so that when the inverter fails you can manually cut frequency operation, because the output voltage can not be applied, frequency and frequency have a solid interlock.
4) Ground the inverter;
The drive is properly grounded is an important means to improve system stability, noise suppression capabilities. Grounding resistance grounding terminal of the inverter as small as possible, the section of the ground wire is not less than 4mm, length does not exceed 5m. Inverter grounding and ground power equipment should be separate, not common ground. Shield end of the signal cable to the ground terminal of the inverter and the other end float. Electrical communication between the drive and the control cabinet.
Inverter control cabinet design:
The drive should be installed in the control cabinet, control cabinet design should pay attention to the following questions
1) heat problems: inverter heat is generated by the internal losses. In various parts of the inverter losses mainly in the primary circuit, accounting for about 98 percent, accounting for 2% of the control circuit. In order to ensure reliable operation of the inverter normally be the inverter cooling fan cooling we usually use; the inverter built-in fan inside the box can drive away the heat, if the fan is not working properly, you should immediately stop the inverter operation; power inverter also need to add a fan in the control cabinet, the control cabinet to be designed wind tunnel, all you want to set the air filter inlet and exhaust smooth, avoiding the formation of a vortex in the cabinet, in a fixed position to form dust accumulation; according to the inverter manual ventilation to select the matching fan, fan installation should pay attention to earthquake problems.
2) electromagnetic interference problems:
I. drive at work because of the rectifier and inverter, generated around a lot of electromagnetic interference, these high-frequency electromagnetic waves in the vicinity of the instrument, the instrument has a certain degree of interference, and will generate high harmonics, the high-order harmonics access to the entire supply network through the power supply circuit, thereby affecting other instruments. If you drive a lot of power over 25% of the entire system, you need to consider measures to control the power of the interference.
II. When the system has high impact loads such as welding, electroplating power supply, inverter itself because of the emergence of interference protection, consider the entire system of power quality problems.
3) protection issues to be aware of the following points:
I. waterproof and condensation: If you drive on the site, you need to pay attention to the inverter cabinet party does not have a pipe flanges or other leak in the vicinity of the inverter can not have a splash of water, in short, to be at the scene of the cabinet Protection class IP43 the above.
Dust II: All you want to set the air filter inlet barrier flocculent debris into the air filter should be designed removable for easy cleaning and maintenance. Dust mesh network based on the specific circumstances of the scene to determine, at the junction with the air filter around to deal with tight control cabinet.
III anti-corrosive gases: In the chemical industry, this situation is more common, frequency counters can now be placed in the control room.
Inverter Wiring specifications:
Signal lines and power lines must be routed separately: When using the analog signal for remote control inverter, in order to reduce interference from analog converter and other devices, set to control the drive signal line and strong electrical circuit (main circuit and sequence loops) separate traces. Distance should be at least 30cm. Even in the control cabinet, also have to maintain this connection specification. Control back to the line between the signal and the inverter shall not exceed 50m.
Signal lines and power lines must be placed separately in different metals or metal hose pipes inside: PLC and inverter connected to a signal line, if not placed in a metal pipe, vulnerable to interference of the inverter and the external device; and because the inverter no built-in reactors, so the input and output stages of the inverter power line will have a strong external interference, thus placing the signal line metal pipe or metal hose has to be extended to the control terminal of the inverter in order to ensure that the signal line completely separated from the power lines.
1) analog control signal lines should use shielded twisted-pair wire, wire sizes for 0.75mm2. When wiring must be noted that the cable stripping as short as possible (about 5-7mm), while the subsequent stripping shield wrapped with insulation tape to prevent contact with the shield introduction of interference with other devices.
2) In order to improve the ease and reliability of the connection, it is recommended to use the pressure bar signal line terminals.
Operation and setting of the drive parameters:
Set the parameters of the inverter and more, each parameter has a certain range of options, often encountered due to the use of the individual parameters are set incorrectly, resulting in the phenomenon of the drive does not work.
Control: namely speed control, torque control, PID control, or otherwise. After taking control, generally based on the control accuracy, the need for static or dynamic identification.
The lowest operating frequency: the minimum speed motor, the motor is running at low speed, its thermal performance is poor, long-running motor at low speeds, it will cause the motor to burn. Also at low speed, it also increases the current in the cable, the cable will lead to heat generation.
Maximum operating frequency: general inverter maximum frequency to 60Hz, and some even to 400 Hz, high frequency will cause the motor at high speed, which is General Motors, its not long over-bearing fixed speed operation, the motor rotor is able to withstand the centrifugal force.
Carrier frequency: the higher the higher harmonic components of the carrier frequency setting is larger, and the length of this cable, electrical heating, cable heating inverter heat and other factors are closely related.
Motor parameters: Drive setting power, current, voltage, speed, the maximum frequency of the motor in the parameters, these parameters can be obtained directly from the motor nameplate.
Hopping: at a certain frequency, there is a resonance phenomenon may occur, particularly in the entire apparatus is relatively high; in the control of the compressor to avoid surge point of the compressor.
Common failure analysis:
1) overcurrent fault: overcurrent fault can be divided into acceleration, deceleration, constant speed overcurrent. It may be due to inverter deceleration time is too short, the load is mutated, the uneven distribution of the load, output short circuit causes. Then generally by extending the acceleration and deceleration time, reduce the load of mutations, plus dynamic braking components, load distribution design, the line to be checked. If you disconnect the drive load or overcurrent fault, indicating that the drive inverter circuit has a ring, you need to replace the drive.
2) overload fault: overload fault including the frequency overload and motor overload. It may be the acceleration time is too short, the grid voltage is too low, overloading and other causes. Generally by extending the acceleration time, prolonged braking time, check the grid voltage. Overloaded, the selected motor and the drive can not drag the load, it may be due to a mechanical cause poor lubrication. The former must be replaced as powerful motor and inverter; if the latter will have to carry out maintenance on production machinery.
3) Brown: Description Power inverter input section there is a problem, you need to check before they can run.