Line reactor question

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ptonsparky

ptonsparky

Tom
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
I received the single phase line reactor for my home well vfd.
Used my older than some of you Fluke 43B to take some recordings. Voltage and current sine waves at panel. Nothing noticeably different before and after.

Today, I was checking the HZ with a Fluke 87 and noticed that A1 to A2, line side, had 60Hz. C1 to C2, load side had 120 Hz with C1 or C2 to EG had 2.56 Khz.

Can I assume the LR is doing what it is designed for, or was I taking meaningless measurements?

Hoping the next time, I press the test button on an AFCI it doesn't throw sparks and fail.
 
The load side C1 -C2 readings are representative of the harmonics created by the VFD rectifier, although 120Hz (2nd harmonic) should have cancelled out if it is a 240V single phase input drive. Was the motor running when you tested? I’d think not, so you are not reading the real current harmonics or their effects on voltage harmonics. In a perfect situation, the current harmonics will be about 70% absorbed as heat in the reactor, which may be why you don’t see them on the line side. If the motor was running, you would see 5th and 7th harmonics (300 and 420Hz), and if it is a single phase input, some 3rd and 9th. Even order current harmonics cancel each other out, multiples of 3 (triplen) harmonics do in a 3 phase system.

The C to G readings are the common mode noise created by the VFD and if the motor WAS running, might indicate a poor ground from the motor to the drive. You want that motor ground to terminate DIRECTLY to the VFD ground terminal. If it goes anywhere else first, it spreads everywhere as it tries to return to its source, the drive transistors. If the motor wasn’t running, that’s just the CM noise from the internal SMPS of the main board of the drive, powering up its own electronics. There is likely virtually no amplitude on that, but the 87 is sensitive enough to pick it up.
 
Line reactor is installed line side or load side? Assuming line side since you said single phase.

The line reactor is essentially a short for slow moving 60 Hz sinewave. No loss or effect at 60 Hz would be a correct result. E = L di / dt. For slow di/dt, x L = low E, Voltage drop through the inductor.

For fast di / dt, switching transients, nearby lightning strike, turn on transients, the line reactor should have the effect of dropping Voltage rather than passing corresponding high current, for the fast available imposed high Voltage transient.

60 Hz is about 5 milliseconds for a quarter cycle and should be shorted (for 60 cycle sinewave) by the line reactor. Transients 2 or 3 orders of magnitude faster, few microseconds, the line reactor is an impedance and tends to drop Voltage, for non sinewave fast transients.

Drive output, the outputs are typically much faster PWM square wave, could be 4 to 12 kHz carrier wave, and needs the inductance of the motor windings to recreate the slow sinewave in the motor. Inductor, line reactor, at the outputs, for when the motor is not close to the drive, mitigate the fast di/dt of the drive square wave output. Instead it builds internal magnetic field and lets the stored energy back out in the next half cycle, slowing and smoothing the drive output.

If you want to see the reactor do something on meter, you could try driving it with 20 kHz, and it should open (and heat up).
 
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