Power Meters, what have you used them for , what kind of circuits?

[danny davis]

Power Meters, what have you used them for , what kind of circuits?

What were you measuring when using a power meter?

 

[tpetar]

Power Meters, what have you used them for , what kind of circuits?

What were you measuring when using a power meter?

Power expressed combination of voltage and current together.


Based on power metering you pay electricity each month.

https://en.wikipedia.org/wiki/Electricity_meter

https://www.google.rs/search?q=powe...65,d.Yms&fp=e419cb0dbc637c07&biw=1024&bih=608

 

[danny davis]

Those digital power meters I know, it's for electronic test technicians

Power meters measure harmonics and other things

 

[danny davis]

What harmonics are clean and what harmonics are dirty?

Are the clean harmonics 1,3,5,8?
the dirty harmonics 2,4,6,7?

The AC outlet from the wall has harmonics too

The AC outlet is 60 hz

The harmonics should be what for a clean AC outlet 60hz signal?

 

[chuckey]

A clean 60 HZ will have no harmonics. Any level of harmonics are unwanted. A supply becomes " dirty" when the harmonics exceed what you require for your purposes.
Frank

 

[danny davis]

So a linear power supply has harmonics? Does a switching power supply have harmonics?

 

[chuckey]

A linear power supply takes AC or DC in and produces DC out. DC has no harmonics. A harmonic is a multiple of a sine wave, i.e. 2F, 3F, 4F etc. if F = 0, then 2F = 0, 3F = 0....
A switching power supply can produce AC or DC output. there cannot be any harmonics of DC. If it produces AC, then it might also produce 2F, 3F etc, i.e. harmonics. if it is not well engineered it might produce harmonics of its internal switching frequencies, which will be unrelated to the actual AC it is producing.
Frank

 

[danny davis]

The output of a dc to ac invertor has harmonics going to a non linear load. The 7th harmonic is the most important one why? The ac waveform on the output of the invertor looks fussy or has fine hairs on the ac sine waveform these are the harmonics. Non linear loads have harmonics?

 

[chuckey]

"The 7th harmonic is the most important one why?", You say its the most importent, you tell us why?
"looks fussy or has fine hairs on the ac sine", these hairs", are multiples of the PWM carrier frequency, and should be filtered out.
Frank

 

[danny davis]

The 3rd , 7th, 13th harmonics is the most important because when you use filters to level out the 3rd, 7th, 13th harmonics is turns a square waveform into a sine waveform

A power factor of 0.7 is what phase shift degree?
A power factor of 1 is what phase shift degree?

A power factor is a phase shift/degree

Harmonics are caused by the power supply filter caps voltage to current phase shift ,and switching, switching frequency?

Linear load has Zero power factor

A Capacitance load has a power factor of 0.7 or 1 or other?

A Inductive load has a power factor of 0.7, 1 or other?

A Capacitance load has which harmonics?
A Inductive load has which harmonics?

Non Linear loads has harmonics , why?

A Non Linear load sets the power factor?

 

[chuckey]

PF - .7 angle = 35 degrees
PF = 1 angle = 0 degrees

A purely capacitive or inductive load has a PF = 0

PF = real power (watts)/total power (V X A ) = cos Phi = angle between real and total power.

Frank

 

[danny davis]

PF - .7 angle = 35 degrees

How did you get the 35 degrees? what formula

A purely capacitive or inductive load has a PF = 0

No, phase shift at all? zero

 

[chuckey]

1. Wrong answer P.F = Cos Phi, so Phi = cos ^-1 .7 ~45 degrees. Its about 40 years since I did this at College and I got my tans and coss mixed up
2. PF= 0 because Phi = 90 degrees
Try :- https://en.wikipedia.org/wiki/Power_factor for more details
Frank

 

[danny davis]

So a 0.7 Power factor is 45 degrees, that means the voltage and current are 45 degrees?

When a unit or UPS says 0.7 Power factor, does it mean the unit is causing this power factor or a non linear load hooked up to it?

 

[chuckey]

1. Yes
2. For a UPS, do you mean it consumes power with a PF of .7, or it can cope with a load with a PF of .7 ?
Frank

 

[danny davis]

Only cope with a load that is 0.7 Not a load that is a power factor of 1 , but what does this mean

- - - Updated - - -

It's says that if u apply a load less than 0.7 Power factor it will damage the output of the unit. The power factor has something to do on how much current the output of the unit can handle on a non linear load right?

 

[chuckey]

No you have it the wrong way around. It can cope with a PF .7 ->1. If the PF < .7, the out of phase current upsets the regulator in it. A PF of .7 is poor, the mains generators will only accept a PF > .9.
Frank

 

[danny davis]

If the PF < .7, the out of phase current upsets the regulator in it.

Why does the regulator get upset when the current is out of phase?

Is the Non Linear load changing the PF? making it greater or less than PF .7?

How do you know what your non linear loads PF value is?

 

[chuckey]

danny davis , first you must learn about PF in ordinary AC circuits. Once you have under stood this then you could move onto PF of non-linear loads. if you had read the Wiki link, they talk about PF of non-linear loads.
Frank

 

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