microcontroller AT89C51based power factor meter &correction

[dhaval]

HELLO Everybody
i m trying to make a power factor meter & correction unit using
microcontroller.
so as an input i need to take input from line directly-then to step
down it in allowable range.
ten i need to use a sine to sqyare wave converter- to make it
compatible to microcontroller.
this step down &conversion process is not difficult as far as voltage
is concerned but for current it is some wt complex can anybody help me
in this regards-should i use C.T.(current transformer) &then current to
voltage converter-or somthing else would be better.

thank u for reading this message.

 

[[email protected]]

i m trying to make a power factor meter & correction unit using
microcontroller.

.... but for current it is some wt complex can anybody help me

in this regards-should i use C.T.(current transformer) &then current to
voltage converter

Usually one uses a series sense resistor (the current transformer works
best at high currents,
but doesn't know the DC current, which is important in a power-factor
situation).
Aim for a voltage drop of maybe 0.100 volts at full current rating.
One can get
'isolation amplifiers' that can handle the line isolation issue, or you
could make
your own isolated power supply, use amplifiers and voltage/frequency
conversion and
optoisolators or transformers to connect to your microprocessor.

If full current is over 10A, the sense voltage times current can
self-heat the series
resistor, so some high currents are sensed using Hall effect sensors to
probe the
magnetic field around the conductor.

 

[Frank-Christian Kruegel]

HELLO Everybody
i m trying to make a power factor meter & correction unit using
microcontroller.

Read this!

http://www.maxim-ic.com/solutions/electricity_metering_system/index.mvp


Mit freundlichen Grüßen

Frank-Christian Krügel

 

[Tim Wescott]

HELLO Everybody
i m trying to make a power factor meter & correction unit using
microcontroller.
so as an input i need to take input from line directly-then to step
down it in allowable range.
ten i need to use a sine to sqyare wave converter- to make it
compatible to microcontroller.
this step down &conversion process is not difficult as far as voltage
is concerned but for current it is some wt complex can anybody help me
in this regards-should i use C.T.(current transformer) &then current to
voltage converter-or somthing else would be better.

thank u for reading this message.

"Power Factor" means the degree of mismatch between the current and
voltage. This is often taken to just mean the phase mismatch between
the sine waves, but for "real" power factor correction you should
probably be monitoring the voltage and current out to the 5th harmonic
(i.e. sample at 1000Hz) and doing some (gasp) real math.

If you're just interested in switching in reactive loads to correct that
fundamental then you may be able to get by with your sine-to-square
converter and timers in the chip, however.

As already mentioned, for the actual detection of volts and amps you can:

1. Use isolation amplifiers on voltage and current.
2. Run your whole circuit on the line side and simply step down the
voltage then either use a current sense resistor, hall effect,
or a current transformer and resistor to sense the current.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html