Variable frequency drives (VFDs) are widely used as core equipment for industrial motor drives in applications such as fans, pumps, compressors, and conveyor belts. However, the rectifier bridge and IGBT switching devices inside a VFD inevitably generate harmonic interference and voltage stress during operation. These issues typically manifest as: excessive harmonics on the input side, low power factor, increased motor noise on the output side, higher eddy-current losses, and accelerated insulation aging. These are not equipment failures, but inherent characteristics of VFD operation – and they can be effectively addressed with the right AC reactors.
Scenario 1: Input Reactor – The "Guardian" on the Grid Side
Issues on the Input Side
- The VFD rectifier bridge generates characteristic harmonics such as 5th, 7th, etc., causing grid voltage distortion
- Harmonics lower the grid power factor and interfere with sensitive equipment such as meters and PLCs (measurement errors, signal distortion, false actions)
- Inrush current during power-on impacts the rectifier bridge and DC bus capacitors, affecting equipment lifespan
- Problems are more prominent when grid impedance is low or multiple VFDs are connected in parallel
How the Input Reactor Solves These Issues
- Suppresses harmonics: Filters high-order harmonics generated by rectification, reducing harmonic current by 30%-40%, smoothing the input current waveform
- Limits inrush current: Suppresses surge current during power-on, with peak current reduction up to 60% or more, protecting the rectifier bridge and capacitors
- Improves power factor: Increases the power factor to 0.75-0.85, reducing line losses
- Bidirectional anti-interference: Prevents grid noise from entering the VFD, and also prevents VFD harmonics from feeding back into the grid
SHINHOM Solution
- Standard solutions for 380V and 690V systems
- Voltage drop options: 2% or 4%
- Rated current covers 5A to 1250A
- Flexible selection based on grid conditions and filtering requirements
Scenario 2: Output Reactor – The "Smoothing Filter" on the Motor Side
Issues on the Output Side
- PWM output voltage contains high-frequency harmonics with high dv/dt (voltage change rate), accelerating motor insulation aging and shortening motor life by 30%-50%
- High-frequency harmonics cause core vibration, increasing motor noise
- Eddy-current losses increase, leading to higher temperature rise and reduced efficiency
- When motor cables exceed 50 metres, voltage reflection occurs, creating peak overvoltage that can damage equipment
- Harmonics generate leakage current through distributed capacitance, affecting system safety
How the Output Reactor Solves These Issues
- Smooths the output voltage waveform: Reduces dv/dt, protecting motor insulation and extending motor life
- Reduces motor noise: Suppresses core vibration caused by high-frequency harmonics
- Reduces eddy-current losses: Suppresses high-frequency components that generate eddy currents inside the motor, improving efficiency
- Compensates for long cable distributed capacitance: Supports cable lengths from 100m to 400m; special designs up to 2000m
- Protects VFD power devices: Reduces the impact of harmonic reflection on IGBTs
SHINHOM Solution
- Provides 1% and 2% voltage drop options
- Adapts to different motor cable lengths and dv/dt protection requirements
- Effectively reduces motor eddy-current losses and leakage current
Selection Guidelines and Supporting Solutions
Input reactors and output reactors address issues on different sides of the VFD – grid-side harmonics and motor-side high-frequency stress. In applications where both the grid and the motor need protection, they are often deployed together.
Core Parameter Selection Table
| Selection Parameter | Description | Typical Range |
|---|---|---|
| System Voltage | VFD rated voltage | 380V / 690V |
| Rated Current | Continuous operating current | 5A–1250A |
| Reactor Type | Input side / Output side | Input: 2% or 4% voltage drop; Output: 1% or 2% voltage drop |
| Application Conditions | Cable length, harmonic requirements | Customised based on actual operating conditions |
SHINHOM Process Features
- Foil winding structure: Low DCR, reduced losses
- Class F insulation: Suitable for industrial environments
- VPI (Vacuum Pressure Impregnation) process: Low noise, long-term stability
- Core material options: Silicon steel, ferrite, amorphous cores
For selection recommendations tailored to your specific VFD system parameters, please contact the technical team.
📧 Email: sales@shinhom.com
🌐 Website: www.shinhom.com/
🔗 Product Details: AC Reactor Series