The frequency converter is a power control device that utilizes the on-off function of the power semiconductor device to convert the power frequency power source to another frequency.
Using frequency converter to affect the motorWhen using the inverter to run, what is the starting current and starting torque of the motor? With the inverter running, the starting current is limited to 150% or less of the rated current (125% to 200% depending on the model) as the motor speeds up the frequency and voltage accordingly. When starting with the power frequency power supply directly, the starting current is 6~7 times. Therefore, mechanical and electrical impact will occur. The inverter drive can be started smoothly (the starting time becomes longer). The starting current is 1.2~1.5 times the rated current and the starting torque is 70%~120% of the rated torque. For the inverter with the torque automatic enhancement function, the starting torque is more than 100%, and it can be started with full load.
Is it possible to get greater braking force?The energy regenerated from the motor is stored in the filter capacitor of the inverter. Due to the relationship between the capacity of the capacitor and the withstand voltage, the regenerative braking force of the general inverter is about 10% to 20% of the rated torque. If using optional brake unit, it can reach 50%~100%.
Please explain the protection function of the inverterThe protection functions can be divided into the following two categories: (1) Corrective actions are automatically performed after detection of abnormal conditions, such as overcurrent stall prevention and regenerative overvoltage stall prevention. (2) Block the power semiconductor device PWM control signal after detecting the abnormality, so that the motor will automatically stop. Such as over-current cut-off, regenerative over-voltage cut-off, semiconductor cooling fan overheating and instantaneous power failure protection.
How inverter protection worksWhy does the protection function of the inverter operate when the continuous load of the clutch is used? When the clutch is used to connect the load, the motor rapidly changes from the no-load state to the area where the slip rate is large at the moment of connection, and the large current that flows causes the inverter to trip overcurrent and cannot operate.
Frequency converter termination reasonIn the same factory, a large motor moves together and the inverter stops during operation. Why? When the motor starts, the starting current corresponding to the capacity will flow. The Transformer on the stator side of the motor will generate a voltage drop. When the motor capacity is large, the pressure drop will also have a large effect. The inverter connected to the same transformer will make undervoltage or instantaneous stop. As a result of the judgment, the protection function (IPE) may occasionally act to stop the operation.
Is there any limit to the mounting direction when installing the inverter?The structure of the inside and the back of the inverter considers the cooling effect. The relationship between the upper and the lower is also important for ventilation. Therefore, take the longitudinal position of the unit type in the tray and hung on the wall, and install it as vertically as possible.
Is it possible to use soft start?Is it possible to use a soft start without putting the motor directly into a fixed frequency inverter? It is possible to operate at very low frequencies, but if the given frequency is high then the conditions for direct start with the commercial frequency power supply are similar. A large starting current (6 to 7 times the rated current) will flow, and the motor cannot be started because the inverter cuts off the overcurrent.
Operational issuesWhat should you watch out for when the motor is running above 60Hz? When operating at more than 60Hz, pay attention to the following: (1) The machine and the device must operate sufficiently at this speed (mechanical strength, noise, vibration, etc.). (2) The motor enters the constant power output range, and its output torque must be able to maintain the work (shaft, pump, etc. shaft output power in proportion to the cube speed increase, so a little increase in speed should also pay attention to). (3) Bearing life issues should be fully considered. (4) For motors of medium-capacity and above, especially 2-pole motors, it is necessary to carefully discuss with the manufacturer when operating above 60Hz.
Can the frequency converter drive the gear motor?According to the structure and lubrication of the reducer, there are a number of issues that need attention. The maximum limit of 70~80Hz can be considered in the structure of the gear. When oil lubrication is used, the continuous operation at low speed is related to the damage of the gear.
Can the inverter drive a single motor?Can the inverter be used to drive a single-phase motor? Can I use single-phase power? Machine basically can not be used. For single-phase motors with governor switch start-up type, the auxiliary winding will be burned when the speed range is below the operating point; for capacitive start-up or capacitor operation, capacitor explosion will be induced. The frequency converter usually has a 3-phase power supply, but for a small capacity, it also has a single-phase power-running type.
What to watch out for when using a motor with brakeBrake excitation circuit power should be taken from the input side of the inverter. If the brake is operating when the inverter is outputting power, the overcurrent will be cut off. Therefore, the brake must be operated after the inverter stops outputting.
Motor does not moveI want to use a frequency converter to drive a motor with a capacitor for improving power factor. However, the motor does not move. This explains why the inverter's current flows into the capacitor for improving the power factor. Because the charging current causes the inverter over-current (OCT), it cannot start. As a countermeasure, please operate the capacitor after it is removed, or even improve the power factor. It is effective to connect the AC reactor to the input side of the inverter.
How long is the life of the inverter?Although inverters are stationary devices, they also have consumer devices such as filter capacitors and cooling fans. If these inverters are regularly maintained, they are expected to have a lifetime of more than 10 years.
Installation directionIs there any limit to the mounting direction when installing the inverter? Should be basically stored in the disk, the problem is that the use of fully enclosed structure of the disk size, space, cost is relatively high. The measures include: (1) The design of the disc should be based on the heat dissipation required by the actual device; (2) The use of aluminum fins, fin coolant, etc. to increase the cooling area; (3) The use of heat pipes. In addition, a type in which the reverse side of the inverter can be exposed has been developed.
Energy-saving principle of frequency conversion speed-regulating energy-saving device 1. Frequency conversion energy-savingAccording to fluid mechanics, P (power) = Q (flow) ╳ H (pressure). The flow Q is proportional to the primary speed of the rotational speed N. The pressure H is proportional to the square of the rotational speed N, and the power P is proportional to the cube of the rotational speed N. If the efficiency of the pump is constant, when the flow rate needs to be adjusted to decrease, the speed N can decrease proportionally, and at this time, the output power P of the shaft decreases. That is, the relationship between the power consumption of the water pump motor and the rotational speed is approximately established. For example: a pump motor power is 55KW, when the speed drops to 4/5 of the original speed, its power consumption is 28.16KW, saving 48.8%, when the speed drops to 1/2 of the original speed, its power consumption The amount is 6.875KW, saving 87.5%.
2, power factor compensation energyReactive power not only increases the line loss and heat generation of the equipment, but more importantly, the reduction of the power factor leads to the reduction of the active power of the grid, a large amount of reactive power is consumed in the line, the equipment is used inefficiently, and the waste is serious. Formula P=S ╳COSФ, Q=S╳SINФ, where S-visible power, P-active power, Q-reactive power, COSФ-power factor, it can be seen that the larger the COSФ, the greater the active power P, the power factor of the ordinary water pump motor is Between 0.6-0.7, after using the frequency conversion speed control device, due to the effect of the internal filter capacitor of the frequency converter, COSФ≈1, thus reducing the reactive power loss and increasing the active power of the power grid.
3, soft start energySince the motor is a direct start or Y/D start, the starting current is equal to (4-7) times the rated current, which will cause serious impact on the electromechanical equipment and the power supply grid, and it will also impose excessive demands on the capacity of the power grid. The high current and vibration cause great damage to the baffle and the valve, which is extremely unfavorable for the service life of the equipment and the pipeline. After the inverter energy-saving device is used, the use of the soft-start function of the inverter will start the starting current from zero, and the maximum value will not exceed the rated current, reducing the impact on the power grid and the requirements for the power supply capacity, and prolonging the use of equipment and valves. life. Save equipment maintenance costs. Inverter can save power This is an indelible fact, in some cases can save more than 40%, but in some cases will be less than the inverter is not wasted! Inverter achieves energy saving through light load step-down. Dragging torque load will not change much because of the rotation speed. Even if the voltage is reduced, there will not be much, so the energy saving is very weak, but it is different when used in fan environment, when it needs more At small moments of wind, the motor will reduce the speed. We know that the energy consumption of the fan is proportional to the 1.7th power of the speed, so the torque of the motor will drop sharply and the energy saving effect will be obvious. If we are used in oil wells, we will waste more electricity by using braking resistors on the return journey to waste a lot of energy. Of course, if the environmental requirements must be adjusted, the inverter energy-saving effect is still more obvious. If the speed is not adjustable, the inverter will not save power and only improve the power factor. 1. If two identical motors are operating in the 50Hz power frequency state, one uses the inverter, one does not, and the speed and torque are under the rated state of the motor, then the inverter can also save power? How much can you save? A: In this case, the inverter can only improve the power factor and it cannot save power. 2. If the torque of the two motors does not reach the motor's rated torque (frequency, speed is the same as 50HZ), how much power can the inverter save? Answer: If the automatic energy-saving operation is used, the inverter can run at a lower pressure at this time, which can save some electric energy, but the power saving is not obvious. 3, the same conditions, how much can be saved under no-load conditions, which provinces of these three states more? A: Drag-type load no-load status can not save much power.
Open-frame Switching Power Modules
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