Inverters
What is a Frequency Inverter? How Does a Frequency Inverter Work?
Frequency inverters are extremely important in many industrial automation and control systems. They help control electric motors accurately and flexibly according to usage needs, increasing production efficiency, assisting businesses to save electricity, and saving costs.
To better understand this product line, please read the short article below!
What is inverter?
Frequency inverters in English are called Inverters. They are electronic devices that convert the frequency and application of alternating current or fixed direction at the input of alternating current with adjustable voltage and frequency at the output.
Thanks to this ability, frequency inverters can allow users to control the facility’s speed accurately and flexibly, opening up many diverse applications in life.
The inverter adjusts the base speed of a single-phase or three-phase motor by controlling the frequency and application of the power supply to the motor. Based on the following formula:
Ns = 120f/p
Where:
- Ns: Base speed
- f: Power frequency
- p: Number of poles of the motor
As you can see, the number of pole pairs p is fixed, so you can only change the current frequency to change the motor speed.
[image]
Structure and operating principle
The inverter configuration is made up of the following main components:
Main parts:
- Control panel
- Control board
- Power board
- Bypass contactor
- DC bus
- Inverter screen
- Variable frequency
- Cooling fan
In which there are critical electronic circuits such as:
- Circuit editing
- Noise filter circuit
- Circuit flow
- Control thread
[image]
The inverter operates based on the following basic principles:
- Converting AC to DC: First, the 1-phase or 3-phase AC power from the power supply will be restored and filtered by the inverter into a flat DC power source through diode bridge rectifiers and capacitors. The inverter will store this DC voltage in the DC bus series-connected capacitors.
[image]
- Modulation: This DC power source will be modulated by electronic circuits to create a square wave with variable frequency and amplitude (usually a PWM modulator).
- Converting DC to AC: Finally, the square wave will be converted back into a 3-phase AC voltage with the desired frequency and voltage amplitude through inverters that power electronic components such as IGBT, Mosfet, etc. With the increasingly developed science and technology, the switching frequency of these power components can reach ultrasonic frequencies. It helps the motor operate smoothly and, at the same time, reduces losses on the iron core.
[image]
Benefits of inverters
Precise motor speed control
By adjusting the input power frequency, the frequency converter helps to control and improve the working efficiency of the motor flexibly. It allows the motor speed to be adjusted flexibly, smoothly, and continuously, mainly in applications such as crushers, conveyors, etc.
Save energy
When the motor operates at a low load, the frequency converter automatically reduces the power, helping to save significant energy. At the same time, it helps to increase motor life.
Motor protection
Due to the optimal voltage and frequency control, the frequency converter provides better protection for the motor against problems such as thermal overload, phase loss, overvoltage, Undervoltage, etc.
Increase accuracy and product quality
The frequency converter with the vector control method can control torque independently of speed, helping to increase accuracy in production processes. The inverter also helps stabilize speed and torque, ensuring consistent product quality and increasing output.
Reduce noise and vibration
The inverter helps to reduce noise and vibration when the motor starts and stops, creating a good, quiet working environment for workers.
Increase reliability
The motor speed transmission system on the inverter can be adjusted more reliably than traditional mechanical methods, such as using valves, gears, louvers, or turbines to control speed and flow.
Soft start
The inverter helps to start the motor from slow to fast gradually. It helps reduce mechanical shock (due to high starting current) and reduce wear on the motor, belt, or gear. When the inverter starts the motor running (the motor is loaded), the motor does not start suddenly, thus reducing the possibility of damage to the insulation or windings inside the motor.
Starting the motor with the inverter at low speed helps the motor to carry heavy loads while still ensuring safety and efficiency.
High power factor
The power factor cosφ is a substantial quantity in the power system, indicating the efficiency level in using electricity. A power system with cosφ closer to 1 means that the system is using the electrical energy source very efficiently. When the load decreases, the motor’s power factor is deficient, which means that the reactive power from the motor is increasing.
There are many methods to improve the power factor cosφ of the system, including:
- Three-phase capacitor banks or reactive power compensation cabinets compensate for the inductive power of inductive loads.
- Using inverters: Adjust the wave shape of the current supplied to the motor. Inverters can minimize harmonic components caused by non-linear loads, thereby improving the power factor.
Currently, there are many inverter lines with high power factor such as Yaskawa U1000 (cosφ = 0.98), Yaskawa GA700 (cosφ = 0.95), Yaskawa A1000 (cosφ = 0.95), …
Slip energy recovery
The primary power supply to the Rotor by the Stator is called the air gap power Pg. The mechanical energy is developed by:
Pm = Pg – sPg
[image]
Applications of inverters in the industry
Variable frequency converters are widely used in applications in many different industrial and civil sectors. Here are some typical applications:
Textile industry: Control the speed of weaving machines, stabilize yarn tension, avoid yarn breakage, and ensure fabric quality.
Paper industry: Control the speed of rolling machines, paper-cutting machines
Food industry:
- Adjust the conveyor speed to suit the production process, ensuring food hygiene and safety.
- Adjust the mixer speed to achieve uniform transmission of the mixture.
[image]
Construction industry: Adjust the mixer’s speed to achieve the concrete mixture’s uniformity. Change the flow and pressure of the pump to meet the needs of use.
Chemical industry:
- Adjust the speed of the mixer by adjusting the voltage and frequency to achieve the uniformity of the chemical solutions.
- Change the flow and pressure of the pump to transport chemicals.
Automotive industry:
- Adjust the speed of the conveyor belt to match the assembly process.
- Adjust the speed and torque of the testing machine to check the performance of automobile parts.
Wastewater treatment industry:
- Adjust the flow and pressure of the pump to treat wastewater effectively.
- Adjust the fan speed to ensure good ventilation for the treatment tanks.
Solar power: Grid-connected inverters convert electrical energy from pure DC to 3-phase electricity synchronized with the grid. Because electricity from renewable energy sources is unstable, it depends significantly on weather and climate. Therefore, inverters with integrated power supplies (batteries, UPS, etc.) are used to connect to the industrial grid.
With applications such as cranes, elevators, air compressors, and HVAC systems, … Inverters help replace traditional stepless control mechanisms in industrial machines.
The best inverter brands on the market
Yaskawa inverter
Yaskawa Electric is one of the world’s leading corporations in manufacturing and supplying products in electric drives and industrial robots. Headquartered in Kitakyushu, Fukuoka, Japan, Yaskawa has more than a century of experience developing and manufacturing advanced automation solutions.
Main products
- Yaskawa inverter
- Industrial robots
- Servo motor
[image]
Siemens Inverters
Siemens is a world-leading industrial group with a long history (170 years) and reputation in manufacturing and providing industrial automation solutions, including inverters. With a combination of advanced technology and many years of experience, Siemens has become one of the most reliable inverter suppliers.
Siemens inverter product lines stand out.
- Sinamics V20
- Sinamics G120
- Sinamics S120
[image]
Nidec Inverter
Nidec is one of the world’s leading corporations producing electric motors and transmission equipment. By 2017, Nidec had completed the acquisition of Control Techniques, which was officially developing a new industry in inverter manufacturing.
With various products, from micro motors to large industrial motors, Nidec has affirmed its position in the automation field.
Some prominent Nidec inverter product lines include:
- Nidec C300
- Nidec F300
- Nidec F600
- Nidec H300
- Nidec M600
[image]
V&T Inverter
V&T Drive Technology Co., Ltd. is one of the leading inverter manufacturers in China. Established in 2006, V&T has grown enormously and become a prestigious brand in control and automation.
Main products include:
- V&T Inverter
- Servo Drive and Servo Motor
- PLC (Programmable Logic Controller)
[image]
In addition to the above brands, there are many other famous brands, such as LS, Fuji, Mitsubishi, etc. For more details, readers can read more articles about the most renowned inverter brands today.
Types of inverters
Inverters can be classified in many different ways; below are three types of inverters according to the input voltage.
1-phase 220V inverter
This type of inverter can adjust the frequency and voltage of single-phase alternating current, converting from a 1-phase 220V source to a three-phase source with adjustable frequency and voltage. Thanks to that, we can flexibly control the speed and torque of a 3-phase motor.
This type of inverter is often used in areas where there is no three-phase power available.
3-phase 220V inverter
A 3-phase 220V inverter is an effective solution to control the speed and torque of a three-phase motor.
It adjusts the frequency and voltage of a 3-phase current, converting from the grid power source to a source with adjustable frequency and voltage.
3-phase 380V inverter
Similarly, the 3-phase 380V inverter changes the frequency and voltage of three-phase AC, converting from a 380V 3-phase grid source to create a three-phase current with adjustable frequency and voltage.
Where to buy genuine inverters?
Nam Phuong Viet Technology Joint Stock Company (NPV) distributes inverter product lines from major brands such as Yaskawa Inverter, Siemens Inverter, and V&T Inverter, … in Vietnam.
With more than 14 years of development, NPV has received the trust and cooperation of customers nationwide. We specialize in providing products and developing leading solutions in the Vietnamese market in the field of Automation, design – construction – and installation of Electrical Panels & Cable Trays.
For any questions, please contact Hotline 0903 803 645.