What is the function of the inverter DC reactor? What are the interference modes of the inverter?

What is frequency conversion resolution? What is its significance?

For digital control inverters, even if the frequency command is an analog signal, the output frequency is given in steps. The minimum unit of this step difference is called the frequency conversion resolution. The frequency conversion resolution is usually 0.015~0.5Hz. For example, if the resolution is 0.5Hz, then the upper 23Hz can be changed to 23.5, 24.0 Hz, so the action of the motor is also followed in steps. This will cause problems for purposes such as continuous winding control. In this case, if the resolution is about 0.015Hz, for a 4-level motor, a step difference of less than 1r/min can also be fully adapted. In addition, some models have different given resolutions and output resolutions.

Are there any restrictions on the installation direction when installing the inverter?

The structure inside and on the back of the inverter takes the cooling effect into consideration. The relationship between the top and the bottom is also important for ventilation. Therefore, for the unit type in the tray or hung on the wall, the vertical position is taken and installed as vertically as possible.

Is it possible to directly connect the motor to a fixed-frequency inverter without using soft starting?

It is possible at very low frequencies, but if the given frequency is high, the conditions are similar to those of direct starting with industrial frequency power supply. A large starting current (6 to 7 times the rated current) will flow, and the motor cannot start because the inverter cuts off the overcurrent.

What should I pay attention to when the motor runs at more than 60Hz?

When operating at speeds exceeding 60 Hz, the following points should be noted: (1) The machinery and equipment must be able to operate at this speed (mechanical strength, noise, vibration, etc.). (2) The motor must enter the constant power output range, and its output torque must be able to maintain operation (the shaft output power of fans, pumps, etc. increases proportionally with the cube of the speed, so attention should also be paid when the speed increases slightly). (3) The life of the bearings should be fully considered. (4) For motors with medium capacity or above, especially 2-pole motors, careful discussions should be held with the manufacturer when operating at above 60 Hz.

Depending on the structure and lubrication method of the reducer, several issues need to be noted. In terms of gear structure, 70~80Hz can usually be considered as the maximum limit. When oil lubrication is used, continuous operation at low speed may cause damage to the gears.

Can a frequency converter be used to drive a single-phase motor? Can it use a single-phase power supply?

Basically, it cannot be used. For single-phase motors with speed regulator switch start, the auxiliary winding will be burned in the speed regulation range below the working point; for capacitor start or capacitor operation, it will induce capacitor explosion. The power supply of the inverter is usually 3-phase, but for small capacity, there are also models that use single-phase power supply to operate.

How much power does the inverter itself consume?

It depends on the inverter model, operating status, and frequency of use, but it is difficult to answer. However, the inverter efficiency below 60Hz is about 94%~96%, and the loss can be estimated based on this. However, for built-in regenerative braking (FR-K) inverters, if the loss during braking is also taken into account, the power consumption will increase, and attention must be paid to the design of the operation panel.

Why can't it be used for continuous operation in the entire range of 6~60Hz?

Generally, motors are cooled by external fans mounted on the shaft or blades on the rotor end rings. If the speed is reduced, the cooling effect decreases, and thus the motor cannot withstand the same heat as high-speed operation. The load torque at low speeds must be reduced, or a large-capacity inverter and motor combination must be used, or a dedicated motor must be used.

What should I pay attention to when using a motor with a brake?

The power supply of the brake excitation circuit should be taken from the input side of the inverter. If the brake is activated when the inverter is outputting power, it will cause overcurrent cutoff. Therefore, the brake should be activated after the inverter stops outputting.

I want to use a frequency converter to drive a motor with a capacitor to improve the power factor, but the motor does not move.

The inverter current flows into the capacitor used to improve the power factor. Since its charging current causes the inverter to overcurrent (OCT), it cannot start. As a countermeasure, please remove the capacitor and operate it. As for improving the power factor, it is effective to connect an AC inductor on the input side of the inverter.

What is the lifespan of a frequency converter?

Although the inverter is a static device, it also has consumable components such as filter capacitors and cooling fans. If they are maintained regularly, they can be expected to have a lifespan of more than 10 years.

The inverter has a cooling fan built into it. What is the direction of the wind? What happens if the fan breaks down?

For small capacity, there are also models without cooling fans. For models with fans, the wind direction is from bottom to top, so the place where the inverter is installed, do not place mechanical equipment that hinders the suction and exhaust above or below. Also, do not place heat-sensitive parts above the inverter. When the fan fails, protection is provided by the fan stop detection or the overheat detection on the cooling fan.

Filter capacitors are consumables, so how do you determine their lifespan?

The capacitance of capacitors used as filter capacitors decreases gradually over time. The capacitance is measured regularly and the life is determined based on when it reaches 85% of the rated capacity of the product.

Are there any restrictions on the installation direction when installing a frequency converter?

The heat dissipation should be basically stored in the disk. The problem is that the disk with a fully enclosed structure is large in size, occupies a large space, and is relatively expensive. The measures include: (1) The design of the disk should be based on the heat dissipation required by the actual device; (2) Use aluminum heat sinks, fin coolants, etc. to increase the cooling area.

What is the function of the inverter DC reactor?

Reduce the high-order harmonic interference of the input current and improve the power factor of the input power supply.

What is the function of the inverter accessory sine filter?

Sine filters allow the inverter to be operated with longer motor cables and are also suitable for circuits with an intermediate transformer between the inverter and the motor.

What is the resistance value of the given potentiometer of the frequency converter?

The resistance of the given potentiometer of the frequency converter is generally 1KΩ to 10KΩ.

What interference methods does the inverter have and how are they generally handled?

1. Transmission mode: (1) Radiated interference; (2) Conducted interference 2. Anti-interference measures: For interference signals transmitted by radiation, they are mainly weakened by wiring and shielding the radiation source and the interfered line. For interference signals transmitted by lines, they are mainly handled by installing filters, reactors or magnetic rings on the input and output sides of the inverter. The specific methods and precautions are as follows: (1) The signal line and the power line should be vertically crossed or wired in separate slots. (2) Do not use wires of different metals to connect each other. (3) The shielding tube (layer) should be reliably grounded and ensure continuous and reliable grounding over the entire length. (4) Twisted pair shielded cables should be used in signal circuits. (5) The grounding point of the shielding layer should be as far away from the inverter as possible and separated from the inverter grounding point. (6) The magnetic ring can be used on the input power line and output line of the inverter. The specific method is: the input line is wound 4 times in the same direction, and the output line is wound 3 times in the same direction. When winding, pay attention to keep the magnetic ring as close to the inverter as possible. (7) Generally, shielding and other anti-interference measures can be taken for the interfered equipment and instruments.

I want to increase the speed of the existing conveyor belt and run it at 80Hz. How should I choose the capacity of the inverter?

The power consumed by the conveyor belt is proportional to the speed. Therefore, if you want to run it at 80HZ, the power of the inverter and the motor must be increased in proportion to 80HZ/50HZ, which means a 60% increase in capacity.

What is the difference between using PWM and VVC+?

In VVC, the control circuit uses a mathematical model to calculate the optimal motor excitation when the motor load changes and compensates for the load. In addition, the synchronous 60° PWM method integrated in the ASIC circuit determines the optimal switching time of the inverter semiconductor devices (IGBTs).

Why can't the inverter be used as a variable frequency power supply?

The entire circuit of the variable frequency power supply is composed of AC-DC-AC-filter, so the voltage and current waveforms it outputs are pure sine waves, which are very close to the ideal AC power supply. It can output the voltage and frequency of the power grid in any country in the world. The frequency converter is composed of AC-DC-AC (modulation wave) and other circuits. The standard name of the frequency converter should be variable frequency speed regulator. The waveform of its output voltage is a pulse square wave, and there are many harmonic components. The voltage and frequency change proportionally at the same time and cannot be adjusted separately, which does not meet the requirements of AC power supply. In principle, it cannot be used as a power supply, and is generally only used for speed regulation of three-phase asynchronous motors.