Selecting a Line Reactor for Industrial VFD Applications
The benefits of the right line reactor – for drives and motors.
A line reactor can enhance performance, life expectancy and efficiency for motors and drives. Line reactors serve as a current limiting device for harmonic and transient waveforms, and can make a tremendous impact. Nuisance tripping, heat, noise, and premature failure are a few problems that can typically be resolved with the added impedance provided by a line reactor.
The added impedance of the line reactor lowers the current peak while extending the wave further over time. Line reactors are usually rated by the percent impedance (Z) they will add to the circuit (1.5%, 3%, 5%). A good rule of thumb for most industrial applications is 3%.
The percent impedance can provide an indication as to how much voltage drop occurs across the reactor, and is calculated by:
%Z = [(Voltage Drop x 100)/Applied Voltage] x √3.
Reactors can be applied to the line and load side of a VFD, each with numerous benefits.
A few of those benefits include:
Line circuit – minimizing harmonic distortion
- Reduce tripping in switchgear (solid state sensing devices).
- Reduce harmonic peaks generated by drive.
Reducing VFD Faults
- Reduce tripping from line sags and peaks
- Reduces Current surges from Voltage Transients
Extending Motor Life
- Lower temperatures (up to 20⁰ C).
- Reduced noise from PWM, by 3-6db.
- Reducing impact of reflected wave.
Selecting a Line Reactor for VFD applications
There are several line reactors on the market from very reputable suppliers.
When looking for you next line reactor, be sure to consider:
- Insulation class – look for 200⁰ C insulation or better.
- Expect a minimum of a 115⁰ C heat rise.
- Ask for VPI (vacuum pressure impregnation) construction.
- Reactors should be designed for both line and load side use, with no de-rating.
Hammond RM-Series Line Reactors
Hammond makes a fantastic line reactor. It not only meets the requirements suggested below, but also:
- Maintains 95% of its inductance at 150% load.
- Can be operated at 50⁰ C (122⁰ F) for up to 24 hours.
- Is short circuit tested (tested at 25 times rated current for 2 seconds)!
