Line Reactors & Inductors
AMP Magnetics is an independent manufacturer’s representative for specialized domestic manufacturers of 3-phase line reactors, load reactors, and precision DC power inductors.
Mitigate Harmonics, Nuisance Tripping, and dv/dt Motor Breakdown
Variable frequency drives draw non-sinusoidal current pulses that distort line voltage and stress utility supplies. On the motor side, high-frequency IGBT inverter switching generates rapid voltage rise times (dv/dt) and reflected wave phenomena that degrade motor winding insulation and ruin bearings.
As a manufacturer’s representative, AMP Magnetics provides direct access to plant engineers who build ruggedized air-gapped iron core reactors designed to absorb line disturbances, damp harmonic spikes, and extend motor lifespan.
Reactor & Inductor Configurations
Our represented principals manufacture magnetic choke components across these core configurations:
| Component Class | Typical Impedance | Current Ratings | Operational Function & Placement |
|---|---|---|---|
| Line Reactors (Input) | 3% or 5% Standard | 2A to 1,200A+ (600V Max) | Installed upstream between the power source and the VFD. Suppresses utility line surges, mitigates cross-talk, and reduces VFD input THD-i. |
| Load Reactors (Output) | 3% Standard | 2A to 1,200A+ | Installed between the VFD and AC induction motor. Damps peak voltage spikes on long cable leads (typically > 50 ft), reduces motor acoustic noise, and lowers operating temperatures. |
| dv/dt Output Filters | Specialized LC Network | Up to 1,000A | Slows voltage rise time (< 200V/μs) to protect non-inverter-duty motors and lead lengths up to 1,000 feet from catastrophic insulation punch-through. |
| DC Link Chokes | Application Tailored | 10A to 800A DC | Mounted in the VFD intermediate DC bus. Smooths DC ripple current, improves input power factor to > 0.90, and reduces AC line harmonics. |
| Harmonic Detuned Chokes | 5.67%, 7%, 14% | Sized to capacitor bank | Connected in series with power factor correction capacitors to prevent electrical resonance at 5th, 7th, or 11th harmonic frequencies. |
When to Specify 3% Impedance
Recommended for general-purpose drive installations where the power feed is relatively stable and clean. Provides sufficient surge attenuation to prevent nuisance drive tripping while maintaining minimal voltage drop at full load.
- Standard line surge buffering
- Basic harmonic current reduction (approx. 40-45% THD-i)
- Minimal system voltage drop (~1.5-2%)
When to Specify 5% Impedance
Essential for stiff power grids (low source impedance), facilities operating adjacent to large welding or arc loads, or applications requiring strict compliance with preliminary IEEE 519 targets before active filtering.
- High-fault capacity utility connections
- Superior harmonic reduction (down to ~30-35% THD-i)
- Required on generator-fed and multi-drive shared buses
Need Pricing or a Custom Inductance Sizing?
Provide your drive horsepower, full-load amps, voltage, and lead length for an immediate technical review and factory quote.
Request Reactor QuoteQuestions we get asked about Reactors & Inductors
Should I specify a 3% or 5% impedance reactor?
Five percent gives better harmonic reduction and transient attenuation but costs about five percent of the voltage available to the motor at full load. On variable-torque loads such as fans and centrifugal pumps that rarely matters. On a constant-torque application already running near full load at rated speed, three percent is usually the safer choice.
What is the difference between a line reactor and a load reactor?
Position determines function. A line reactor sits on the drive input and protects the drive from inrush, line transients and nuisance overvoltage trips while reducing input harmonic current. A load reactor sits on the drive output and slows the rate of voltage rise reaching the motor, protecting stator insulation on long cable runs. They are not interchangeable.
When do I need a DC link choke instead of a line reactor?
A DC link choke gives harmonic reduction roughly equivalent to a 3 percent line reactor without any fundamental voltage drop, so no motor torque is lost. Because it sits behind the rectifier it offers no protection against line-side voltage transients. Choose it where torque margin is tight and transient protection is handled separately.
How long can motor leads be before a load reactor is needed?
On 480 volt systems, reflected wave effects generally become a concern beyond roughly 50 feet with a standard motor, and a load reactor is commonly recommended past 100 to 200 feet. Beyond about 600 feet a sine wave filter is often required. Thresholds tighten at 600 volts and with motors not rated to NEMA MG1 Part 31.