[syhprum (OP)]

This gadget cuts your electric bill by 90% legaly How?

[evan_au]

What is it good for?

Absolutely nothing! (pretty much...)

It's much like the power factor correction capacitors that used to be installed in fluorescent lights.
- But you can save more money by using LED lights that don't need power factor correction...

https://www.sabireviews.com/motex-review/

[vhfpmr]

This gadget cuts your electric bill

No it doesn't.

1. Domestic premises aren't required to have power factor correction because they don't need it.
2. Whether they do or not, it won't affect your bill because electricity meters read true power not apparent power.
3. When PFC is required, it needs to be the correct amount for the load, applied at the load, a random amount that doesn't disconnect when the load is disconnected is just as likely to increase the load current as reduce it.

[syhprum (OP)]

While the domestic load will be of a restive nature except for a few small transformers for battery chargers etc one would expect filament lamps where there is a rapid change of resistance as the Tungsten wire heats to some extent to look like capacitors.
Has anyone with suitable equipment measured the PF of filament lamps ?
 

[evan_au]

a rapid change of resistance ...to same extent to look like capacitors.

I'm afraid not.

A capacitor stores charge as the voltage increases away from 0, and delivers it back to the source as the voltage starts to reduce towards 0. In a perfect capacitor, the current is 90° out of phase with the voltage. A perfect capacitor draws current, but does not dissipate any power.

A resistive load (like a tungsten filament) does not store any charge (maybe a few Pico Farads of stray capacitance). In a perfect resistor, the current is in-phase with the voltage. It turns all the incoming current x voltage into dissipated power.

[syhprum (OP)]

It would be interesting to connect a filament lamp via an inductor and a simulated negative resistor to see if any oscillation occurs