Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

reactor purpose for variable speed motor

Does anyone know the purpose of the inline reactor (looks like a transformer) when it is installed on a variable speed blower motor? Normally I see these installed on 1 hp motors and I was wondering it's purpose, and would it be the same part for a 16 pin variable speed motor (2.3) , as it would be for an X13 motor? Thanks to all


  • Jamie Hall
    Jamie Hall Member Posts: 20,500
    Kind of a guess -- but I would guess that it is there to choke high frequency switching harmonics from the motor so they don't get back into the power line. Anything which uses a switching power supply or uses switching for speed control -- like you motor -- generates a lot of very high frequency hash, and if that gets into the power line it creates all sorts of problems for other equipment on the same electrical drop from the power company.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    JUGHNE Member Posts: 10,322
    In addition to furnace blower motors, every Mini Split inverter has one also.....anyway the ones do that I have had the misfortune to have to trouble shoot :(

    Easiest ones are a shorted compressor...new system time after 13 years.
  • ron
    ron Member Posts: 308
    google inline reactor for vfd

    vfd = variable frequency drive... a type of motor controller that drives an electric motor by varying the frequency and voltage of its power supply. The VFD also has the capacity to control ramp-up and ramp-down of the motor during start or stop, respectively.
    A line reactor is an optional component that can be added to a drive system to protect the VFD and other devices from power surges and transients. A line reactor is essentially an inductor—a coil of wire that forms a magnetic field as current flows through it.
    Line reactors are electromagnetic devices used as inductors to protect variable frequency drives (VFDs) and other devices from electrical disturbances such as voltage spikes, surges, and transients. Line reactors can limit your current flow and harmful harmonics from the drive

    A line reactor (also called an input reactor) is installed before the VFD and protects the drive, while a load reactor (also called an output reactor) is installed after the VFD and protects the motor. When a current wave form is not sinusoidal, it's said to contain harmonics.
  • ron
    ron Member Posts: 308
    also google sizing and connecting line reactor for more technical info that might help answer would it be the same part for a 16 pin variable speed motor (2.3) , as it would be for an X13 motor? On that specifically i can at best point you in a generally correct direction.
  • ratio
    ratio Member Posts: 3,336
    Load reactors are a thing too.

    Also mind that a 'rotary' compressor is not a 3 phase compressor. It's basically a giant BLDC motor, with a permanent magnet armature. The controller pulses the windings on & off—and reverses the magnetic polarity—to move the armature. They can not be reversed by swapping leads, or at least the ones I've come across can't.