Walk through a plant, and you will hear four names for what looks like the same box on the wall: VFD, frequency inverter, frequency converter, and servo drive. Buyers often ask if these are four different products. Some of the names describe one thing, and one of them describes a different job.
Utility power arrives at a fixed frequency. A drive lets a motor run at other speeds, so one motor can handle work that changes. Drives have also become compact and versatile, since microprocessors replaced older solid-state elements.
You can find them in petroleum, chemical, hoisting, water supply, plastics, textiles, printing, and packing. With that many uses, the naming gets messy.
The Short Answer
VFD, frequency inverter, and frequency converter point to the same family of devices. A servo drive is the one with a different focus: position control and precision.
- VFD (Variable Frequency Drive): An electronic system that controls an AC induction motor. It manages torque, speed, and direction.
- Frequency inverter: The everyday name for the same kind of drive. Veikong builds its VFD series inverters with SPWM, sensorless vector control, and vector and torque control. The general purpose VFD range goes up to 1000kW.
- Frequency converter: Another name for the same job, often used when talking about pumps and energy savings.
- Servo drive: A drive built around position control and encoder interfaces, such as spindle orientation on a CNC machine.
What Is a VFD?
A VFD starts a motor smoothly and brings it up to the desired speed at a controlled acceleration rate. It also controls torque and direction. That means one motor can serve jobs that need different speeds.
A VFD system has three parts:
- AC motor: Commonly a three-phase induction motor.
- Main drive controller: Solid-state electronics with a DC-link or filter, a switch, and an inverter section.
- Monitoring and control interface: The way to start and stop the motor, adjust speed, and change direction.
People usually pick a VFD for these reasons:
- To control the speed of a manufacturing process
- To get a smooth start and steady acceleration
- To save energy where load torque and power vary
- To improve control of speed, temperature, tension, pressure and torque
- To run a motor in special patterns that reduce mechanical and electrical stress
Frequency Inverter and Frequency Converter: Same Idea, Different Words
Veikong’s own pages show how loosely these terms get used. The pump page talks about frequency converters, while the product lines are called frequency inverters and VFDs. They describe the same drive doing the same work.
Pumps make a clear example. When a drive slows a pump, the pump curve shifts down. The system reaches the same reduced flow it would get from a valve, such as 700 GPM down from 1200 GPM, but at a lower pressure.
Lower pressure can mean longer pump seal life, less impeller wear, and less vibration and noise. Because of the affinity laws, power drops sharply at reduced flow. That drop is where the savings come from.
Typical pump uses include:
- Chilled and hot water pumps
- Condenser water pumps
- Booster pumps
Where a Servo Drive Is Different
The S6 shows what sets a servo drive apart. It is a spindle-dedicated servo drive, built to run the spindle motors of CNC lathes, milling machines, machining centers, and grinders. It brings position control and encoder interfaces that a plain speed drive does not focus on.
Key details of the S6:
- Motor types: IM and PMSM
- Voltage: Three-phase 380V to 480V, or three-phase 200V to 240V
- Power: 2.2kW to 11kW
- Control: SVC and VC
- Communication: Modbus on the S6, EtherCAT on the S6C, M3 bus on the S6M
- Functions: Spindle orientation, position control, full closed-loop application, parameter backup and recovery, and complete fault records
There is also a middle ground. The VFD550I electro-hydraulic servo inverter is made for hydraulic control.
It supports asynchronous and permanent magnet synchronous motors, and it handles pressure control under encoderless vector control with built-in pressure control algorithms. It suits injection molding machines, die-casting machines, and hydraulic stations.
- Power range: 0.7kW to 710kW
- Power saving: Comprehensive saving rate of 20% to 60%
- Pressure control: Overshoot of ≤±1% and steady-state fluctuation of ≤±0.5Bar
Which One Fits Your Machine?
Match the drive to the job:
- Cranes and hoists: A VFD gives smooth start and stop, high starting torque at low speeds, and less wear on the gearbox, brake, and wire rope.
- Spinning frames: A VFD allows adjustable spindle speed and constant yarn tension, with fewer yarn breaks.
- CNC machines: A VFD offers smooth acceleration and deceleration, accurate speed regulation, and programmable speed profiles. For spindle positioning, look at the S6.
- Hydraulic injection molding: The VFD550I is designed for this kind of pressure control.
- Solar water pumping: Veikong’s customized PV pump software delivers 99.9% energy tracking efficiency.
Veikong’s Drive Range at a Glance
- General purpose VFD series: Power range up to 1000kW
- VFD500 PV: Solar pump inverter
- VFD500M: Single-phase 200/240V at 0.4 to 4kW, and three-phase 380/480V at 0.75 to 7.5kW
- VFD510 IP55: 380V from 2.2kW to 45kW or bigger, with IP55 protection
- VFD580: A high-end vector inverter
- VFD550I: Electro-hydraulic servo inverter
- S6: Spindle dedicated servo drive
The range also includes the VFD 500, VFD 530, and VFD 550 AC drives, plus bypass soft starters.
Why Buyers Look at Veikong Electric
Shenzhen VEIKONG Electric Co. Ltd. is an AC drive enterprise founded in 2004. It researches, manufactures, and trades high-, medium-, and low-voltage frequency inverters, with general purpose VFDs available up to 1000kW.
Its R&D and management team brings more than 20 years of experience in research, product development, and quality management.
- Standards: ISO9001 quality management and CE certification, with products that comply with ISO, CE, and IEC standards.
- R&D: 52 technical patents and National High-Tech Enterprise status.
- Testing: A 12-hour power-on aging test in a high-temperature chamber, followed by a final full-load machine test.
- Quality record: A delivery failure rate of 0.5%.
- Warranty: 24 months, with free spare parts for component quality issues.
- Investment: No less than 20% of annual operating profit goes into R&D.
Summary
VFD, frequency inverter, and frequency converter are three names for one kind of drive, which controls the speed, torque, and direction of an AC motor. Veikong’s general purpose VFDs cover power ratings up to 1000kW.
A servo drive such as the S6 goes further with position control, spindle orientation, and encoder interfaces. The VFD550I sits between the two for hydraulic pressure control.
Not sure which drive suits your machine? Send the Veikong team your motor and application details, and they will help you select the right one.