Reactors are primarily used for current limiting, filtering, reactive power compensation, and harmonic suppression. Choosing the right reactor requires consideration of circuit characteristics, load type, system voltage, harmonic content, and other factors. Below is a systematic selection methodology.
1. Define the Core Function of the Reactor
Reactors can be categorized based on application:
| Type | Primary Function | Typical Applications |
|---|---|---|
| Current Limiting Reactor | Limits short-circuit current, protects equipment | Power systems, VFD input/output sides |
| Filter Reactor | Suppresses harmonics, improves power quality | VFDs, UPS, renewable energy grid integration |
| Smoothing Reactor | Reduces DC ripple, stabilizes current | DC drive systems, HVDC transmission |
| Reactive Compensation Reactor | Prevents resonance with capacitors | SVG, SVC, TSC compensation systems |
2. Key Selection Parameters
(1) Rated Current & Voltage
- Rated Current (ININ): Based on maximum load current, including short-term overload capacity.
- Rated Voltage (UNUN): Must match system voltage (e.g., 380V, 690V, 10kV).
(3) Reactance (%)
- Common Reactance Values: 4%, 6%, 7%, 14%, depending on harmonic levels:
- 4%~6%: General industrial use (low harmonics).
- 7%~14%: High-harmonic environments (e.g., VFDs, rectifier loads).
(4) Frequency & Harmonics
- Base Frequency: 50Hz/60Hz.
- Harmonic Environment: Measure THD (Total Harmonic Distortion) to select appropriate reactance.
(5) Cooling Method
| Cooling Method | Applications | Advantages | Disadvantages |
|---|---|---|---|
| Natural Cooling | Low power (<100A) | Simple, maintenance-free | Limited heat dissipation |
| Forced Air Cooling | Medium power (100A–1000A) | Better cooling, compact | Requires fan, noisy |
| Water Cooling | High power (>1000A) | High efficiency, high density | Expensive, needs cooling system |
3. Selection by Application
(1) VFD Input/Output Reactors
- Input Reactor:
- Function: Suppresses grid-side harmonics, protects VFD.
- Reactance: Typically 2%~4% (low harmonics), 5%~7% (high harmonics).
- Output Reactor:
- Function: Reduces dv/dt, protects motor insulation.
- Reactance: Typically 1%~3%.
(2) Renewable Energy (PV/Wind) Filter Reactors
- Function: Suppresses grid harmonics (complies with IEEE 519).
- Reactance: 5%~7% (for 5th/7th harmonics).
(3) Reactive Compensation (SVG/SVC) Reactors
- Function: Prevents capacitor-system resonance.
- Reactance: 6%~7% (usually in series with capacitors).
5. Application Examples
Case 1: Industrial VFD Input Reactor
- Load: 55kW motor, 380V, 50Hz
- Harmonics: THD≈8% (dominant 5th harmonic)
- Selection:
- Reactance: 5%
- Rated Current: 100A (20% margin)
- Cooling: Natural (IP20)
Case 2: Solar Plant Filter Reactor
- System Voltage: 800V DC
- Harmonics: 5th/7th (THD>10%)
- Selection:
- Reactance: 7%
- Inductance: 0.5mH
- Cooling: Forced air (IP54)