Publish Time: 2022-06-29 Origin: Site
The variable frequency drives is a power control device that converts the power frequency power supply into another frequency by using the on-off function of the power semiconductor device. The correct selection of the frequency converter is very critical to the normal operation of the control system. Usually we need to consider the matching problem with the motor, load type, site environment and so on when we select the inverter. Below we will specifically introduce what factors need to be considered when selecting an inverter.
1. Determine the purpose of frequency conversion: constant voltage control or constant current control, etc.
2. The load type of the inverter: such as vane pump or positive displacement pump, etc.. Pay special attention to the performance curve of the load, which determines the method of application.
3. Select the inverter according to the actual working current of the motor
The actual working current of the motor is the most critical factor in the selection of the inverter. When the inverter works for a long time, the output current of the inverter must be greater than the actual working current of the motor. Remember that the motor is usually selected first in the project, and then the inverter is selected according to the motor.
4. Matching between inverter and load
(1) Voltage matching: The rated voltage of the inverter is consistent with the rated voltage of the load.
(2) Current matching: If it is an ordinary centrifugal pump, the rated current of the inverter is consistent with the rated current of the motor. For special loads such as deep water pumps, it is necessary to refer to the motor performance parameters to determine the inverter current and overload capacity with the maximum current.
(3) Torque matching: This situation may occur when a constant torque load or a reduction gear is present.
In general, the inverter drives the constant torque load motor, and the inverter is selected based on the rated current of the motor.
In general, the inverter drives the motors of fans and pumps, and the inverter is selected based on the rated current of the motor.
For a motor that is often overloaded for a short time, it is necessary to calculate the overload period and overload current.
5. If the inverter needs to run with a long cable, measures should be taken to suppress the influence of the long cable to the ground coupling capacitance, so as to avoid insufficient output of the inverter. Therefore, in this case, the capacity of the inverter should be increased by one step or the inverter should be installed in the inverter. An output reactor is installed at the output end.
6. The capacity of the inverter for high-speed motors is slightly larger than that of ordinary motors. Because when using a frequency converter to drive a high-speed motor, due to the small reactance of the high-speed motor, the increase of high-order harmonics will lead to an increase in the output current value.
7. The impact of the site environment
For some special applications, such as high temperature and high altitude, this will cause the derating of the inverter, and the capacity of the inverter should be enlarged by one stop.
(1) Temperature
The operating ambient temperature of the inverter is generally -10 to 40°C. If the ambient temperature is higher than 40°C, the inverter should be derated by 5% for every 1°C increase; The service life is halved, so the problem of the surrounding environment and the heat dissipation of the inverter must be solved.
(2) Altitude
The inverter can output rated power when installed at an altitude below 1000m. At altitudes above 1000m, its output power will drop.
(3) Humidity
The inverter works in an environment with a humidity lower than 90%, the relative humidity of the air is less than or equal to 90%, and there is no condensation. When the humidity is too high and the humidity changes greatly, condensation is likely to occur inside the inverter, and its insulation performance will be greatly reduced, and may even cause a short circuit. If necessary, a desiccant or heater must be added to the box.
(4) Dust
The inverter should not be installed in the occasion with metallic conductive dust. Conductive dust intrusion into the inverter will short-circuit the internal circuit of the inverter, and in severe cases, the inverter will be burned.
Xichielectric mainly provides two kinds of inverters: XFC500 open-loop vector control inverter and CFV9000A series high-voltage inverter.
Features:
(1) This model has a wide range of applications.
(2) Support wall-mounted, embedded, side-by-side, top-bottom and other installation methods.
(3) 132KG/160KP and above models have built-in DC reactor.
(4) Flexible application function expansion, mainly including IO expansion card, PLC expansion card.
(5) Rich communication expansion, CANopen, Profibus, EtherCAT and other communication expansion cards can be connected through the expansion interface.
(6) External LED operation keyboard can be introduced.
(7) All series support common DC busbar and DC power supply.
CFV9000A series high-voltage inverter takes high-speed DSP as the control core, adopts space voltage vector control technology and power unit series multi-level technology. With high reliability, easy operation and high performance as the design goals, it can meet the needs of users for various types of load speed regulation, energy saving, and production process improvement.
Our high-voltage inverter is divided into all-in-one series high-voltage VFD and basic series high-voltage VFD.
All-in-one series high-voltage VFD:
Feature: Based on the two-quadrant synchronous (including permanent magnet synchronous motor)/asynchronous motor platform design, the whole machine integrates control cabinet, power cabinet, transformer cabinet and switching cabinet, which is easy to install
Advantages: Small size, save space; overall transportation, easy installation
Load type: fans, pumps
Basic series high-voltage VFD:
Feature: Based on the two/four-quadrant synchronous (including permanent magnet synchronous motor)/asynchronous motor platform design and unit sealing design, the whole machine is modularly designed, and the production efficiency is high.
Advantage: Modular design of the control system, small harmonics, precise speed regulation, good sealing performance of the power unit, and strong environmental adaptability
Load type: fans, water pumps; elevator, belt conveyor.