Carlos,
Given the statements from vax9000 I did a quick setup with real diode, resistor and Fluke 45 (Am I doing this?)
Multimeter Reads DC 54V DC and 65V AC
If we ask multimeter to do the math: TRMS=sqrt(AC^2+DC^2)
by pressing VAC and VDC simultaneously.
I get 84,5V a lot closer to what we expect, right?
It can be read in page 57 (chapter 4 page 10)
Given the statements from vax9000 I did a quick setup with real diode, resistor and Fluke 45 (Am I doing this?)
Multimeter Reads DC 54V DC and 65V AC
If we ask multimeter to do the math: TRMS=sqrt(AC^2+DC^2)
by pressing VAC and VDC simultaneously.
I get 84,5V a lot closer to what we expect, right?
It can be read in page 57 (chapter 4 page 10)
4fun said:
If you examine the fluke chart I posted...
120 volts rms = 120*1.414 = 169.68 volts peak..
For half wave rectified, 2 volt input, the ac reading is .771, the DC is .636, and the rms is 1.000.
Now, put in 169.68 volts..that is 169.68 / 2 = 84.84 times larger..
So, 84.84 times .771 (the ac reading) = 65.411...expected AC reading is 65.411 volts..you reported 65.
84.84 times the .636 DC reading = 53.95824....you reported 54 volts DC.
And the sqrroot function, at 1.000, will give 84.84 voltsRMS...you reported 84.5.
Summary of your errors:
AC...you were off by .411 volts..
DC...you were off by .04176 volts.
RMS value..you were off by .34 volts..
I'll forgive such sloppy work this time, but please try in the future, to be more accurate...
(nice work)..
poobah said:
As expected..
Cheers, John
That is indeed correct..4fun said:jneutron,
Any mathematician would argue strongly against use of more significant numbers in answer than input.
You have mistaken my tongue in cheek comment about accuracy....perhaps 4 smileys were needed??
Cheers, John
PS..actually, I expected somebody to call me on the diode drop that was missing..
Hi 4fun ,
You are absolutely correct !!!! The measure confirm
all of eletricity theory .
The 45’s settings , too !!!
But , you make me unhappy , because the nice “side”
of this thread was the controversy , that has just ended
with your brilliant demonstration of the answer , by both
ways : theoretic and practical ( lab measures ) . No pro-
blem , we need to create another simple question , with
the same level of controversy . It’s good to teach and
to learn .
No doubt , the correct answer is half power ( 25 Watts ) .
The polemic and controversy that have been generated
by this thread , started by Vax 9000 , with a very , very
simple question , has been VERY , VERY good for all of
us because the knowledge about RMS value of differents
wave’s shape is a fundamental point to all people that likes
or needs to build and design power supplies or power amps .
Congratulations ,
Carlos
You are absolutely correct !!!! The measure confirm
all of eletricity theory .
The 45’s settings , too !!!
But , you make me unhappy , because the nice “side”
of this thread was the controversy , that has just ended
with your brilliant demonstration of the answer , by both
ways : theoretic and practical ( lab measures ) . No pro-
blem , we need to create another simple question , with
the same level of controversy . It’s good to teach and
to learn .
No doubt , the correct answer is half power ( 25 Watts ) .
The polemic and controversy that have been generated
by this thread , started by Vax 9000 , with a very , very
simple question , has been VERY , VERY good for all of
us because the knowledge about RMS value of differents
wave’s shape is a fundamental point to all people that likes
or needs to build and design power supplies or power amps .
Congratulations ,
Carlos
Hi,
The Power Factor Correction (PFC) capacitor is to reduce the phase angle of the load.
Large motors and transformers can use electricity at large phase angles but the heating effect in the supply cables, transformers and generators is related to the peak currents.
High phase angle increases the heating effect for NO USEFULL increase in power delivered.
PFC is not there to block or reduce the DC component whether from even harmonic distortion or from peak waveform shaving.
The Power Factor Correction (PFC) capacitor is to reduce the phase angle of the load.
Large motors and transformers can use electricity at large phase angles but the heating effect in the supply cables, transformers and generators is related to the peak currents.
High phase angle increases the heating effect for NO USEFULL increase in power delivered.
PFC is not there to block or reduce the DC component whether from even harmonic distortion or from peak waveform shaving.
I agree that this is the 'engineering' argument, but the commercial reason is mainly to do with metering.
Why would supply companies worry very much that the power supplied was doing no useful work, as long as they could charge for it? Most suppliers insist on a PF of over 0.85 to ensure that energy is correctly metered.
Take the extreme example: If our diode-equipped soldering iron was one of 1000 in a large factory, all connected in the same way, the facility would be consuming a considerable current which could not be registered by the eddy-current motor driving a standard consumer meter, which responds only to the in-phase AC component).
To put it another way: as you say, high I/V phase angle decreases the work done by, in this case, the meter, but the unregistered power is still available for space-heating or whatever, free of charge.
Why would supply companies worry very much that the power supplied was doing no useful work, as long as they could charge for it? Most suppliers insist on a PF of over 0.85 to ensure that energy is correctly metered.
Take the extreme example: If our diode-equipped soldering iron was one of 1000 in a large factory, all connected in the same way, the facility would be consuming a considerable current which could not be registered by the eddy-current motor driving a standard consumer meter, which responds only to the in-phase AC component).
To put it another way: as you say, high I/V phase angle decreases the work done by, in this case, the meter, but the unregistered power is still available for space-heating or whatever, free of charge.
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