Converter wiring
1. Main circuit wiring
(1) Inverter input (R, S, T), output (U, V, W) must not be connected wrong
(2) The inverter grounding terminal is well grounded (if the factory circuit is zero-ground common, it is necessary to consider a separate ground)
Multiple frequency converters should be grounded, and each frequency converter should be connected to the ground separately. Do not allow the grounding of one frequency converter to be connected to the grounding terminal of another frequency converter and then grounded.
(3) Connect the power input terminal of the inverter to the power supply through the leakage protection switch (leakage switch, air switch should choose a good manufacturer)
2. Wiring of control circuit
(1) The analog control line should use a shielded line, and the shielded end is connected to the common end (COM) of the inverter control circuit, do not connect to the ground end of the inverter (E) or the earth, and the other end is suspended.
(2) The switching control line is allowed not to use the shielded line, but the two wires of the same signal must be twisted together, and the twisting distance of the twisted line should be as small as possible.
Third, improve the power factor of the inverter
In order to improve the power factor or when the installation site is very close to the large capacity power supply, it is necessary to add DC and AC reactors. In addition to improving the power factor, there are the following effects:
(1) Inhibit the inrush current in the input
(2) Reduce the impact of the power supply voltage imbalance
Selection of reactance:
(1) The reactor voltage drop is not greater than 3% of the rated voltage.
(2) When the transformer capacity is greater than 500KVA or the transformer capacity is more than 10 times the frequency converter capacity, a reactor should be equipped.
Fourth, inverter anti-interference
1, external interference to the inverter
Mainly from the power supply line. When the power system is put into other equipment (such as capacitors) or because of the operation of other equipment (such as thyristors and other commutating equipment), it is easy to cause power distortion and damage the switching tube of the inverter. A series of AC reactors in the input circuit of the inverter can effectively suppress the interference from the incoming line.
2, inverter interference to the outside world
(1) Propagation mode of interference signal
The mode of air radiation is external radiation in the form of electromagnetic waves
Electromagnetic induction is induced by inductance between wires
Electrostatic induction mode communication line capacitance and induction
Line propagation mode is propagated through line source network
(2) Anti-interference measures
A Inverter side
Interference signals propagated by induction are attenuated by proper wiring and the use of shielded lines
The interference signal propagated by the line can be attenuated by inserting small inductors into the line
Interference signals propagated by radiation, attenuated by absorption method (radio anti-interference filter)
The filter reactor in series between the output side of the inverter and the motor can not only play an anti-interference role, but also reduce the additional torque caused by higher harmonics and improve the operating characteristics of the motor.
On the output side of the inverter, it is absolutely not allowed to use capacitors to absorb harmonic current.
B Instrument side
Power isolation method The power supply side of the instrument is connected to an isolation transformer
Signal isolation method The signal side is isolated by photoelectric coupler
Five, inverter lightning protection
Lightning protection In the frequency converter, there is generally a lightning absorption network, mainly to prevent the instant lightning intrusion, so that the frequency converter damage. However, in actual work, especially in the case of the overhead introduction of the power line, the absorption network of the inverter alone can not meet the requirements. In active lightning areas, this problem is particularly important, if the power supply is an overhead inlet line, install a frequency conversion dedicated lightning arrester (optional) at the inlet line, or according to the specification requirements in 20m away from the inverter embedded steel pipe for special grounding protection. If the power supply is introduced by cable, the lightning protection system in the control room should be done to prevent lightning from entering and damaging the equipment. The practice shows that this method can solve the problem of lightning strike effectively.
Six, inverter brake parts selection.
1 Brake unit (optional parts)
When the control equipment driven by the inverter needs fast braking, the braking unit should be selected to release the energy that is returned to the DC bus when the motor is braking.
2 Brake resistance (optional)
The braking resistance selection of different power levels of inverters is shown below.
Voltage Level V Motor power kW Resistance Resistance value OHM\/Parallel number Resistance power kW
Motor power kW Resistance Resistance value OHM\/Parallel number Resistance power kW
380 0.75 400 0.25 37 16 9
1.5 400 0.25 45 13.6 9
2.2 250 0.25 55 20\/2 12
3.7 150 0.4 75 13.6\/2 18
5.5 100 0.5 90 20\/3 18
7.5 75 0.8 110 20\/3 18
11 50 1.0 132 20\/4 24
15 40 1.5 160 13.6\/4 36
18.5 30 4.0 200 13.6\/5 45
22 30 4.0 220 13.6\/5 45
30 20 6.0 280 13.6\/6 54
3 Connection of brake components (Example)
Brake resistance installation [up to 7.5kW] Brake control unit installation [up to 11kW]
(2) Inverter debugging, precautions
The basic steps that should be taken in the commissioning of the inverter include no-load test with power supply, no-load operation with motor, trial operation with load, and on-line integration with the host computer, etc. Issues to be noted in completing these steps:
1, before switching on the inverter power, it is necessary to check whether its input and output end meet the requirements of the manual;
2, especially to see if there is new content to increase, carefully read the precautions;
3. Check whether the wiring is correct and tight.
General frequency converters have RUN (RUN), STOP (STOP), programming (PROG), DATA\/ confirm (DATA\/ENTER), increase (UP, ▲), reduce (DOWN, ▼), and other six keys, and the definition of different frequency converters' operation keys is basically the same. In addition, some inverters have function keys such as monitoring (MONTTOR\/DISPLAY), RESET (RESET), inch (JOG), and SHIFT (SHIFT).
First, the inverter is connected to the power supply test run (no motor)
After connecting the power supply, press the RUN button to run the inverter to 50HZ, and use a multimeter to measure the output (U V W) phase voltage of the inverter should be balanced (370V-400V). Press the stop button and then connect the motor cable.
Second, the inverter with motor no-load operation
1. Set the power of the motor and the number of poles, and comprehensively consider the working current of the inverter.
2. Set the maximum output frequency and fundamental frequency of the inverter and set the torque characteristics.
3. Set the inverter to its own keyboard operation mode, press the inch key, run key and stop key, and observe whether the motor is reversed and whether it can start and stop normally.
4. Be familiar with the protection code when the frequency converter fails, observe the factory value of the thermal protection relay, observe the set value of overload protection, and modify it when necessary. 3. Test run with load
1. Manually operate the running stop button of the inverter panel, observe the motor running stop process and the display window of the inverter, and see if there are abnormal phenomena. If there is a phenomenon, change the preset parameters accordingly before running.
2. If the inverter overcurrent protection action occurs in the process of starting and stopping the motor, the acceleration and deceleration time should be reset. The acceleration of the motor in acceleration and deceleration depends on the acceleration torque, and the frequency change rate of the inverter in the starting and braking process is set by the user. If the motor moment of inertia or motor load changes, according to the preset frequency change rate of speed up or deceleration, there may be insufficient acceleration torque, resulting in motor stall, that is, the motor speed and frequency converter output frequency is not coordinated, resulting in overcurrent or overvoltage. Therefore, it is necessary to reasonably set the acceleration and deceleration time according to the motor's moment of inertia and load, so that the frequency change rate of the inverter can be coordinated with the speed change rate of the motor. The way to check whether this setting is reasonable is to first select the acceleration and deceleration time according to experience to set, if there is overcurrent in the startup process, you can appropriately extend the acceleration time; If overcurrent occurs during braking, the deceleration time should be extended appropriately. On the other hand, the acceleration and deceleration time should not be set too long, and too long time will affect the production efficiency, especially when frequent starting and braking.
3. If the inverter is still protected within a limited time, the start\/stop running curve should be changed from a straight line to an S-shaped, U-shaped line or anti-S-shaped, anti-U-shaped line. When the load inertia of the motor is large, longer start and stop time should be used, and the type of running curve should be set according to its load characteristics.
4. If the frequency converter still has operating faults, it should try to increase the protection value of the maximum current, but it cannot cancel the protection, and at least 10%-20% of the protection margin should be left.
5. If the operation failure of the inverter still occurs, the inverter with greater power should be replaced.
6. If the motor driven by the inverter does not reach the preset speed during the startup process, there may be two situations:
(1) The system has an electromechanical resonance, which can be judged from the sound of the motor running. The method of setting the frequency jump value can avoid the resonance point. Generally, the inverter can set three jump points. When the V\/f controlled frequency converter drives the asynchronous motor, in some frequency segments, the current and speed of the motor will oscillate, and the system can not run in serious cases, and even the over-current protection in the acceleration process makes the motor cannot start normally, which is more serious when the motor is light load or the moment of inertia is small. Common frequency converters are equipped with frequency jump function, users can set the jump point and jump width on the V\/f curve according to the frequency point of oscillation in the system. When the motor accelerates, these frequency segments can be automatically skipped to ensure the normal operation of the system.
(2) the torque output capacity of the motor is not enough, different brands of inverter factory parameter Settings are different, under the same conditions, the load capacity is different, it may also be due to the different control methods of the inverter, resulting in the load capacity of the motor is different; Or due to the different output efficiency of the system, the carrying capacity will be different. In this case, the value of the torque lift can be increased. If not, the manual torque lifting function can be used, do not set too large, the temperature rise of the motor will increase at this time. If it is still not possible, a new control method should be used, such as Hitachi inverter using a constant V\/f ratio method, when the start fails to meet the requirements, the speed sensorless space vector control method is used, which has a greater torque output capacity. For fan and pump loads, the curve value of torque reduction should be reduced.
Fourth, the frequency converter is connected to the host computer for system debugging
After the basic manual setting is completed, if there is a host computer in the system, the control line of the frequency converter is directly connected to the control line of the host computer, and the operation mode of the frequency converter should be considered and changed to terminal control. According to the needs of the upper computer system, the range of the frequency signal terminal received by the frequency converter is adjusted to 0-5V or 0-10V, and the response speed of the frequency converter to the analog frequency signal sampling. If an additional monitor head is required, the analog output monitor should be selected and the range of the inverter output monitor terminal should be adjusted.
This situation may be encountered when debugging, after the signal is given by the upper machine, the inverter does not execute. Because some upper computers only accept AC signals, do not accept DC signals, and the control signals of the inverter are mostly DC signals, then you can consider external relays.
(3) Maintenance and maintenance
Due to the changes in the use environment of the inverter, such as the influence of temperature, humidity, smoke, and other factors, as well as the aging of the internal components of the inverter, various failures may occur in the inverter. Therefore, in the process of storage and use, it is necessary to carry out daily inspection of the inverter, and carry out regular maintenance.
1. Daily maintenance
When the inverter is normally turned on, please confirm the following:
1, whether the motor has abnormal sound and vibration.
2. Whether the frequency converter and motor are heating abnormally, and whether the ambient temperature is too high.
3. Whether the load ammeter is the same as the usual value.
4. Whether the cooling fan of the inverter works normally.
Second, regular maintenance
Frequency converter regular maintenance inspection, be sure to cut off the power supply, until the monitor does not show and the main circuit power indicator light is off, can be checked. Check the contents as shown in the table.
Check item Check the solution to abnormal contents
Main loop terminal and control loop terminal screw Tighten the screw with a screwdriver
If there is dust in the heat sink, blow it off with dry compressed air with a pressure of 4~6kg\/cm2
PCB printed circuit board whether there is dust with 4~6kg\/cm2 pressure of dry compressed air to blow away
Check whether the cooling fan generates abnormal sounds or vibrations. Replace the cooling fan
If there is dust in the power element, blow it off with dry compressed air with a pressure of 4~6kg\/cm2
Whether the aluminum electrolytic capacitor is discolored, smelly, or bubbling Replace the aluminum electrolytic capacitor
Fourth, fault detection
OH: The machine is overheating
Overheating is a common failure. When you encounter this situation, you will first think of whether the cooling fan is running, whether the fan is blocked, whether the ambient temperature is too high, the inverter is poorly ventilated, and the temperature detection circuit is faulty.
POFF: undervoltage
Whether the input power supply lacks phase, the input power terminal is loose, and the input power voltage fluctuates greatly. Check whether the rectifier is faulty and the DC voltage is lower than 380V
OU: Overvoltage
We must first eliminate the fault caused by the parameter problem. For example, the deceleration time is too short, the overvoltage caused by the regenerative load (plus the brake unit), then we can look at whether there is a problem with the input voltage, and finally we can look at whether there is a fault in the voltage detection circuit, the general voltage sampling point of the voltage detection circuit is the voltage of the intermediate DC circuit.
OCU, OCS: indicates the overcurrent
This is probably the most common fault in the inverter. We must first eliminate the fault caused by the parameter problem. For example, current limitation, too short acceleration time may lead to the generation of overcurrent. Then we must determine whether there is a problem with the current detection circuit, such as Hall sensor, Hall line fault. Whether the output side of the inverter is short-circuited.
OL: Overload
The acceleration time is too short, the motor load is too heavy, and the motor is stuck.
HE: The current sensor is faulty
The Hall line is not connected properly, the sensor is damaged, and the current detection circuit is faulty.
OCU1: Hardware protection
This is the most common failure. Inverter three-phase output UVW phase short-circuit phenomenon, external electrical equipment interference,IGBT,IPM module damage.
The following is a simple fault test for the main circuit of the inverter:
With the digital multimeter, technicians can simply determine whether the main loop device is damaged according to the figure above. (Mainly rectifier bridge,IGBT,IPM)
For personal safety, it is necessary to ensure that the machine is powered off, and remove the input power lines R, S, T and output lines U, V, W before operation!
First hit the multimeter to the \"secondary tube\" file, and then through the red and black pen of the multimeter according to the following steps:
1. The black pen contacts the negative P() of the DC bus bar, and the red pen contacts R, S, and T successively to record the display value on the multimeter; Then the red pen contact N(-), the black pen contact R, S, T in turn, record the display value of the multimeter; If the six display values are basically balanced, it indicates that there is no problem with the inverter diode rectification or soft start resistance, and on the contrary, the rectifier module or soft start resistance at the corresponding position is damaged, and the phenomenon is: no display.
2. The red pen contacts the negative P() of the DC bus bar, and the black pen contacts U, V, and W in turn to record the display value on the multimeter; Then put the black pen in contact with N(-), and the red pen in turn in contact with U, V, and W to record the display value of the multimeter; If the six display values are basically balanced, it indicates that the inverter IGBT inverter module has no problem, on the contrary, the IGBT inverter module in the corresponding position is damaged, and the phenomenon is: no output or fault.
How to wire the operation control loop of the inverter, how many volts, generally speaking, the circuit of the inverter is mainly divided into two parts, the main loop and the control loop. The wiring diagram of the main circuit is as follows, with three-phase power input and output connected to the motor, brake resistance and control power lamp terminals.
The control loop is the core of the inverter, which mainly includes switching input terminals, relay output terminals, open collector output, analog input, output, 24V power supply, 10V power supply, and communication ports such as 485 interface. Then how the control loop is wired and how many volts are used is determined according to the inverter control mode you choose. For example, we control the start and stop of the inverter using external terminal control, at this time, we only need to short-circuit S1, S2 and com, which is a passive switch, can be controlled by the input terminal of the plc, the output signal Y is connected to S, and the public end is connected. Because it's a passive power supply that doesn't require many volts. For example, the relay output is used to indicate the fault indicator of the inverter, which can be connected to the DC or AC power supply, and the power supply and the indicator are in the normally open output circuit of the relay. Then this 10v power supply is used to control the frequency of the inverter, which is generally used to adjust the output voltage speed by using a potentiometer.
Each brand of inverter control loop wiring method, the required voltage is not the same, this should be completed according to the provisions of the operating manual, including the terminal definition, wiring methods, input and output connection diagram will be very detailed marked, according to the above to wire, I hope to help you!