Cable Length
- Keep the motor cable as short as practical.
- Use shielded cable for long-distance installations.
- Avoid parallel routing with sensitive power or signal cables.
Variable Frequency Drive Manufacturer for Industrial Motor Control
ZHENGXI manufactures Variable Frequency Drives (VFDs) for controlling the speed and torque of AC motors. Our drives are used with pumps, fans, conveyors, compressors, machine tools and other motor-driven equipment.
ZHENGXI supports machinery manufacturers, electrical contractors, panel builders, distributors and industrial users with:
- General-purpose and heavy-duty VFD configurations
- Single-phase and three-phase input options
- 220 V, 380 V and project-specific voltage configurations
- V/F and sensorless vector control
- PID and multi-speed operation
- RS485 communication
- OEM branding and product customization
20+
Years Experience
80+
Countries Exported
OEM & ODM
Supported
14
high-efficiency production lines
Fast
Delivery
24/7
Technical Support
Choose the Right VFD
Different applications require different drive ratings, control methods and protection configurations. Select a solution according to the motor current, power supply, load type and operating environment.
0.75KW-800KW Three Phase Ac Frequency Converter
0.75KW-500KW Three Phase Ac Frequency Converter
0.75KW-200KW Photovoltaic Three-Phase Inverter Cabinet
For higher-power motors or complete project installations, ZHENGXI can provide customized frequency conversion control cabinets with suitable switching, protection, cooling and control components.
U9000 Technical Specifications
The following specifications are based on the standard U9000 platform. Exact values may vary by drive power and configuration.
| Parameter | Standard or Available Configuration |
|---|---|
| Rated input | Three-phase AC 380 V or single-phase AC 220 V class |
| Input frequency | 50/60 Hz |
| Three-phase input range | Approximately AC 360–450 V |
| Single-phase input range | Approximately AC 190–250 V |
| Output voltage | Variable output according to input class |
| Standard output frequency | 0–300 Hz |
| High-frequency version | Up to 3000 Hz on applicable configurations |
| Digital frequency resolution | 0.01 Hz |
| Analog frequency command | 0–10 V DC or 0–20 mA DC |
| Control modes | V/F, advanced V/F, V/F separation and sensorless vector |
| Programmable speeds | Up to 16 stages |
| Communication | RS485; protocol to be confirmed |
| Acceleration/deceleration | Adjustable linear or S-curve |
| Carrier frequency | Approximately 1–16 kHz adjustable |
| Ambient temperature | Approximately −10°C to +40°C |
| Ambient humidity | 5%–95% RH, non-condensing |
| Protection class | IP20 standard |
| Cooling method | Fan-controlled air cooling |
| Installation | Wall-mounted or inside an electrical cabinet |
The final selection should be based on the model datasheet and rated output current rather than this general table alone.
Key VFD Features
⚙️ Stable Motor Speed Control
A VFD adjusts the frequency and voltage supplied to an AC motor, allowing motor speed to match the actual operating requirement instead of running continuously at fixed grid frequency.
🔄 Controlled Starting & Stopping
Adjustable acceleration and deceleration can reduce starting current and mechanical impact on belts, couplings, pumps and other driven equipment.
🎯 Vector Control Options
Sensorless vector control provides improved torque performance and speed stability compared with basic V/F control, especially for changing loads and low-speed torque applications.
📊 Built-In PID Control
PID control automatically adjusts motor speed according to pressure, flow or temperature signals. Common applications include water supply, ventilation and process control.
🛡️ Motor & Drive Protection
Overcurrent
Overvoltage
Undervoltage
Motor Overload
Drive Overheating
Phase Loss
Short Circuit
Stall Prevention
Sensor Feedback Fault
Protection availability and trip thresholds vary by model.
🔗 Automation Integration
RS485 and Modbus communication options allow compatible drives to exchange operating information with PLCs, HMIs and centralized control systems.
RS485
Modbus
PLC
HMI
How We Select a VFD for Your Motor
Customers often begin by asking for a “15 kW VFD” or an “18.5 kW VFD.” Motor power is useful, but it does not provide enough information for reliable selection.
Two motors with the same kW rating can have different currents, efficiencies, torque requirements and operating duties.
ZHENGXI normally evaluates the following factors before recommending a configuration.
Motor Nameplate Current
The VFD’s rated output current must meet or exceed the motor’s rated current under the intended operating conditions.
For example, an 18.5 kW conveyor motor may require a different drive configuration from an 18.5 kW centrifugal pump. The conveyor may need higher starting torque and overload capacity, while the pump normally has a variable-torque load.
ZHENGXI Engineering Note: Do not select a VFD from motor power alone. Send the complete motor nameplate whenever possible.
Input Power Supply
We need to know:
- Single-phase or three-phase input
- Nominal input voltage
- Grid frequency
- Available breaker capacity
- Expected voltage fluctuation
- Utility or generator supply
If the input voltage is frequently outside the drive’s permitted range, the VFD may trip on undervoltage or overvoltage. In locations with unstable power, the incoming supply should be evaluated before installation.
Load Type
| Load Type | Typical Equipment | Selection Priority |
|---|---|---|
| Variable torque | Centrifugal pumps and fans | Energy efficiency and PID control |
| Constant torque | Conveyors, mixers and extruders | Low-speed torque and overload capacity |
| High starting torque | Crushers and loaded conveyors | Heavy-duty rating and vector control |
For a centrifugal pump or fan, basic V/F control may be sufficient. A loaded conveyor or mixer usually benefits from sensorless vector control because it requires stronger torque at low speed.
Acceleration and Deceleration
A large fan may not require high starting torque, but its high inertia can produce a long acceleration and stopping time.
Setting the deceleration time too short may cause DC bus overvoltage. In this case, the correct solution may be:
- A longer deceleration ramp
- DC braking
- A braking resistor
- An external braking unit
- A regenerative drive system
The stopping requirement should therefore be confirmed before selecting the braking accessories.
Installation Environment
The standard IP20 drive must be installed in a clean, dry and adequately ventilated location or inside a suitable electrical cabinet.
Tell us if the installation involves:
- High ambient temperature
- High altitude
- Dust or conductive particles
- Moisture or condensation
- Oil mist
- Corrosive gas
- Outdoor installation
- Restricted cabinet ventilation
High temperature and altitude may require drive derating or a larger power rating.
Application Selection Guide
| Application | Suggested Control | What to Check |
|---|---|---|
| Centrifugal pump | V/F or sensorless vector | Pressure, flow range, PID and minimum speed |
| Fan or blower | V/F | Airflow, operating hours and system resistance |
| Conveyor | Sensorless vector | Loaded starting, torque and acceleration |
| Mixer | Sensorless vector | Low-speed torque and motor cooling |
| Compressor | Application-dependent vector control | Pressure, lubrication and overload |
| CNC spindle | Vector or high-frequency control | Maximum frequency and speed accuracy |
| Winding machine | Vector control | Tension, braking and speed stability |
| Crusher | Heavy-duty vector control | Peak torque and repeated shock loading |
| Hoist | Closed-loop or dedicated hoist drive | Brake control and functional safety |
Cranes, elevators and personnel-carrying equipment require a dedicated safety assessment. A general-purpose VFD should not be selected without checking brake control, feedback, emergency stopping and applicable safety standards.
How a Variable Frequency Drive Works
① Rectifier
Converts incoming AC power into DC power.
② DC Bus
Smooths and stabilizes the rectified DC voltage.
③ Inverter
Uses high-speed semiconductor switches to create adjustable-frequency AC output.
AC Input
→
Rectifier
→
DC Bus
→
Inverter
→
Variable-Frequency AC
→
Motor
⚙️ Changing Frequency Changes Motor Speed
Synchronous Speed = (120 × Output Frequency) ÷ Number of Motor Poles
50 Hz
1500 rpm
1500 rpm
40 Hz
1200 rpm
1200 rpm
30 Hz
900 rpm
900 rpm
Example values are based on a four-pole motor. Actual shaft speed is slightly lower because of motor slip.
📘 Want to Learn More?
For a more detailed explanation of rectifiers, DC buses, IGBTs and PWM, see our guide: How Does a Variable Frequency Drive Work?
V/F Control or Vector Control?
⚙️ V/F Control
Choose when:
- Load is a centrifugal pump or fan
- Extremely accurate speed control is unnecessary
- Starting torque is moderate
- Simple and economical solution is preferred
Maintains a relationship between output voltage and frequency. Suitable for many standard industrial applications.
🔄 Sensorless Vector Control
Choose when:
- Stronger low-speed torque is required
- Load changes during operation
- More stable speed is required
- Driving a conveyor, mixer or processing machine
- Faster torque response is required
Estimates motor flux and torque without an encoder. Correct motor nameplate data and auto-tuning are important.
🎯 Closed-Loop Control
Choose when:
- Accurate low-speed operation is essential
- Full torque is required near zero speed
- Rapid load changes occur
- Encoder feedback is required
- Demanding positioning or tension control is needed
Requires a compatible VFD, encoder and motor-feedback arrangement.
Quick Selection
Pump / Fan → V/F
Conveyor / Mixer → Sensorless Vector
Precision / Feedback → Closed-Loop
Can a VFD Reduce Energy Consumption?
A VFD can reduce energy consumption when a motor does not need to operate continuously at full speed. The greatest energy-saving potential is typically found in centrifugal pumps and fans.
⚡ Pump & Fan Affinity Laws
Flow
∝ Speed
∝ Speed
Pressure
∝ Speed²
∝ Speed²
Power
∝ Speed³
∝ Speed³
Under ideal affinity-law conditions, reducing motor speed can significantly reduce power demand.
📊 What Determines Actual Savings?
- Operating hours
- Required flow or pressure
- Static head
- System resistance
- Existing valves or dampers
- Motor and drive efficiency
- Time spent at partial load
🏭 Other Applications
For conveyors, mixers and machine tools, the main benefits may be process control, soft starting and reduced mechanical shock rather than large energy savings.
⚠️ Important
VFD installation does not automatically guarantee energy savings. A proper evaluation should consider the complete operating duty cycle, including load profile, operating hours and system conditions.
VFD vs. Soft Starter
A VFD and a soft starter can both reduce the impact of motor starting, but they serve different purposes.
| Comparison | Variable Frequency Drive | Soft Starter |
|---|---|---|
| Starting-current control | Yes | Yes |
| Continuous speed control | Yes | No |
| Frequency adjustment | Yes | No |
| Torque control | Available | Limited |
| PID process control | Available | No |
| Energy-saving potential | High in suitable variable-speed loads | Limited after startup |
| Typical application | Adjustable-speed operation | Fixed-speed motor with smooth startup |
| Cost and complexity | Generally higher | Generally lower |
Use a VFD when the motor requires variable speed or continuous process regulation.
Use a soft starter when the motor runs at full speed after startup and only needs reduced starting current and mechanical shock.
Important VFD Installation Considerations
🔌 VFD-to-Motor Cable Length
Long motor cables can increase reflected-wave voltage, leakage current and stress on motor insulation.
Depending on the installation, consider:
- Output reactor
- dV/dt filter
- Sine-wave filter
- Shielded motor cable
- Inverter-duty motor
💡 Tell the supplier the approximate VFD-to-motor distance before ordering.
🌡️ Motor Cooling at Low Speed
A standard shaft-mounted cooling fan provides less cooling when the motor operates at low speed.
For continuous high torque at low frequency, consider:
- Independent cooling fan
- Inverter-duty motor
- Larger motor
- Revised speed range
Particularly important for conveyors, mixers and constant-torque machinery.
📡 Electromagnetic Interference
Rapid semiconductor switching can interfere with sensors, communication cables and control systems if wiring or grounding is incorrect.
- Separate power and signal cables
- Use shielded motor cable when required
- Ground drive and motor correctly
- Keep motor cables away from sensitive wiring
- Use EMC filters where required
Follow the drive manual's wiring instructions.
IEC 61800-3 → EMC requirements
IEC 61800-3 → EMC requirements
〰️ Input Harmonics
A standard VFD rectifier draws non-sinusoidal current. Harmonics can become significant when multiple or high-power drives share the same electrical system.
AC Line Reactor
DC Choke
Passive Filter
Active Filter
Multi-Pulse
AFE Drive
Large projects may require a harmonic study rather than selecting a filter based only on drive power.
⚠️ Output-Side Components
Do Not:
Install ordinary power-factor-correction capacitors between the VFD and motor.
Install ordinary power-factor-correction capacitors between the VFD and motor.
Do Not:
Repeatedly switch an output contactor while the VFD is actively supplying the motor.
Repeatedly switch an output contactor while the VFD is actively supplying the motor.
These practices can damage the VFD or connected components. Follow the manufacturer's wiring and switching requirements.
VFD Protection Functions
🛡️ Protection Functions
Depending on the model and parameter configuration, the U9000 platform can monitor and respond to:
Overcurrent
Overvoltage
Undervoltage
Motor Overload
Module Overheating
Short Circuit
Phase Loss
Parameter Errors
Memory Faults
📊 Real-Time Monitoring
The display can show key operating and diagnostic data, including:
Output Frequency
Output Current
Output Voltage
Motor Speed
DC Bus Voltage
PID Values
Module Temperature
⚠️ Important Installation Note
A VFD does not replace all upstream protection. The installation still requires appropriate circuit protection, isolation and grounding according to the application and local electrical requirements.
Installation & Application Guidance
Motor Cooling
- Ensure adequate ventilation for the motor and VFD.
- Apply the required derating in high-temperature environments.
- Keep cooling paths and air inlets clear.
Harmonics
- A VFD may introduce harmonics into the electrical system.
- Use AC reactors or line chokes where required.
- Consider harmonic filters for sensitive systems.
Application Case Study
Conveyor System in Logistics
Solution
U9000 Series VFD with vector control
Results
18%
Energy Savings
25%
Reduced Maintenance
99.2%
System Availability
Tested Before Shipment
Every VFD undergoes rigorous testing to ensure reliable performance and quality.
- Full-load test
- Performance verification
- Safety and protection test
- Appearance and function inspection
Reliable quality you can trust.
What Our Customers Say
Feedback from equipment buyers, distributors and industrial project partners.
“We installed the ZHENGXI VFDs on several pumps and ventilation fans. The drives were straightforward to set up, and the motors now start much more smoothly than before. Speed adjustment is stable, and the built-in PID function helps us maintain the required pressure without constantly running the motors at full speed.”
[Le Thanh Nam]
“Our conveyor needed reliable low-speed torque and smooth acceleration when starting with a load. After reviewing the motor nameplate and operating conditions, the ZHENGXI team recommended a suitable VFD configuration. The conveyor now starts smoothly, runs steadily at the required speed and causes less mechanical shock to the belt and transmission components.”
[Jorge Martínez]
“We use ZHENGXI VFDs in our industrial machinery and electrical control cabinets. Their compact design makes panel installation easier, while the available terminals and RS485 communication meet our control requirements. ZHENGXI also supports customized branding, documentation and parameter guidance, which is valuable for our OEM projects.”
[Budi Santoso]
FAQ
Can a VFD convert single-phase power to three-phase power?
Yes, if the VFD is designed or correctly rated for single-phase input and its output matches the motor voltage.
A VFD is normally used to operate a compatible motor. It should not automatically be used to power an entire three-phase machine containing multiple motors, transformers and control circuits.
Why does a VFD trip during motor startup?
Possible causes include:
- Insufficient VFD current capacity
- Acceleration time set too short
- Motor parameters entered incorrectly
- Heavy or locked mechanical load
- Low input voltage
- Short circuit or grounding fault
- Unsuitable control mode
- Incorrect current or torque limits
The fault code and operating current should be checked before resetting the drive repeatedly.
Should a VFD be oversized for a heavy-duty load?
Possibly. Equipment that starts under load, requires high low-speed torque or operates with frequent acceleration may need a heavy-duty rating or a larger VFD.
Selection should be based on motor current, overload duration and load characteristics—not a fixed oversizing percentage.
What is the difference between a VFD and a soft starter?
A soft starter controls voltage mainly during motor starting and stopping. The motor normally operates at full grid frequency after startup.
A VFD controls motor frequency and voltage throughout operation, enabling continuous speed regulation. If speed control is unnecessary, a soft starter may be the more economical solution.
What Information Is Required to Replace an Existing VFD?
Provide:
- Existing VFD brand and model
- Input voltage
- Rated output current
- Motor nameplate
- Terminal wiring
- Control signals
- Communication protocol
- Braking arrangement
- Installation dimensions
- Existing parameter backup, if available
A replacement drive must match the electrical and control requirements. Matching only the power rating is not enough.
Can a VFD save electricity?
A VFD can reduce energy use when motor output needs to change during operation. The strongest opportunities are normally found in centrifugal pumps and fans.
Actual savings depend on the speed profile, system curve, operating hours and original control method. The U.S. Department of Energy recommends evaluating the load duty cycle when estimating adjustable-speed drive savings.
Need help selecting a VFD?
Send us the motor nameplate, application, input voltage and required quantity. Our technical team will recommend a suitable configuration.
Welcome Enquiry
Are you looking for reliable suppliers and quality products? Fill out the form and send it to us — we’ll get back to you within 24 hours!We’re not around but we still want to hear from you! Leave us a note
Welcome Enquiry