Power factor calibration inspection by using a Variable Autotransformer VARIAC

[Kiriakos GR]

This personal journey started, by me reading one IEC guideline about digital power meter calibration.
Any single phase power meter / watt matter, this it should be inspected regarding power factor calibration, at the values of 1.000 and at 0.500 PF

My second though was of where I can find such an apparatus, that it can have adjustable Power Factor displacement? 
Power Factor 1.000 = any resistive load and even a common light bulb.
For adjustable Power Factor displacement down to 0.500 we need another and a special load.

Next in line information that I came across, was about calibration inspection of energy meter by the use of phantom power.
And then I did seen a known to me circuit schematic, and this was not other than of my own Variable autotransformer – VARIAC.

The in-depth electrical theory about variable autotransformer, it mention that at very light loads, bellow 10% or lower,  the magnetizing current  of the autotransformer  will lagging power factor as low as 0.5 PF.

I did activate right away my Variac that is a Powerstat 226U, 2KV model, from Superior Electric brand in the USA.
My Powerstat 226U this includes a NORMAL and a BOOST (step-up mode).

I did connect Powerstat 226U as this to be a load, at my GM86 (plug in power meter), with four digits PF resolution.
Superior Electric's standby power specification for Powerstat 226U (without load connected) this is approximately 9 Watt (230AC).
 
Originally I started testing NORMAL mode, this operating as INPUT voltage limiter.
By turning VARIAC shaft from minimum to Maximum I recorder bellow values.

Watt Minimum: 7.78W --   PF 0.601 -- 58 mA
Watt Maximum: 10.25W --   PF 0.685 -- 65 mA

The miracle started to happen as soon I activated the BOOST mode = a much higher magnetizing current.

Watt Minimum:       10.61W --   PF 0.462 -- 96 mA

Shaft adjustment at:  11.62W --  PF 0.501 -- 100 mA

Watt Maximum:     14.23W --   PF 0.570  --  106 mA

And here came my moment so and I to scream Eureka (word), an exclamation for a discovery or invention.

In conclusion:
I could never believe that power analysis at my own variable transformer, this helped me to understand of how valuable this is, as testing apparatus at single phase power meter calibration!! 


https://www.ittsb.eu/forum/index.php?topic=1240.0

[overvolt]

Excellent discovery! 

Variable autotransformer with step-up mode, they will gain now a higher preference.