With the continuous improvement of industrial automation, frequency converters have been widely used. Energy conservation and environmental protection are the core of China's industrial economic development. While pointing the way for the sustainable development of China's industry, they are also effectively driving the sustainable development of China's frequency converter industry, enabling the industry to continuously expand its market share and become an important cornerstone of China's industrial economic development with its strong development momentum.
Variable frequency drive (VFD) energy saving is mainly used in situations where it is necessary to change the characteristics of the drive machinery by varying the speed of the AC motor to meet production process requirements. It is frequently used in fans and water pumps. When a motor can only operate at its rated speed, its drive machinery can only operate at a certain rated speed.
1. Speed control of ordinary motors :
The speed of a three-phase asynchronous motor can be controlled by changing its input voltage and frequency. In ordinary motors, the temperature rises significantly at low speeds due to decreased cooling fan efficiency; therefore, the motor load should be reduced according to the frequency.
2. Capable of high-speed operation:
The standard power supply frequency is 50Hz, which remains constant. Inverters, however, can output frequencies up to 650Hz (EH600A series). The EH600H series can reach a maximum output frequency of 1500Hz.
Simply increasing the frequency of a general-purpose motor cannot achieve high speed; mechanical strength must also be considered. At high speeds, the inverter's carrier frequency is high, requiring derating of the inverter, etc.
3. Capable of soft start and soft stop:
The acceleration and deceleration time of the frequency converter can be set arbitrarily between 0.1 and 6500.0 seconds. Appropriate acceleration and deceleration times need to be set for the frequency converter during operation.
4. Quick and accurate start-up and shutdown:
The starting current is low, resulting in less motor heat generation. Capacity determines acceleration and deceleration times; therefore, the capacity rating of the motor and frequency converter should be increased, and the ratio of acceleration/deceleration time to load should be adjusted.
5. Can easily achieve forward and reverse rotation:
The direction switching is performed by IGBTs, thus eliminating the losses associated with traditional contactors and enabling reliable interlocking operation. When used in elevators, a motor with a holding brake should be used, and a mechanical holding mechanism should be provided when changing direction.
6. Can be electrically braked:
Because mechanical energy can be converted into electrical energy within the frequency converter during deceleration, the motor will automatically brake. Applying DC braking to the motor at zero speed can quickly stop a freely running motor. The frequency converter only provides 20% braking force. To increase braking force, an external braking unit and braking resistor are required. Frequency converters with built-in braking units only require an external braking resistor.
7. Motor speed adjustment is possible in harsh environments:
Because three-phase asynchronous motors can be used, explosion-proof, submersible, or specially shaped motors can be easily adopted. Explosion-proof motors should be tested and certified for explosion protection in conjunction with the frequency converter. Our company's general-purpose frequency converters are not explosion-proof.
8. One frequency converter can control the speed of multiple motors:
A frequency converter can simultaneously regulate the speed of multiple motors. The rated current of the frequency converter should be greater than 1.1 times the total current of the motors. At the same frequency, the speed will vary due to differences in the characteristics of asynchronous motors and the load. Each motor should also be protected by a heating overload relay.
9. The power supply capacity for starting the motor does not need to be too large:
Unlike power frequency power supplies, which have large starting currents (5-6 times the motor's rated current), variable frequency drives (VFDs) start up with a maximum current of no more than 100-150% of the motor's rated current.
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