Experiment
1
9
Lpatt,
Var
,
VoltAmpere,
and
Power'
Factor
OBJECTlVE
To
study
the
relationship
among
wait,
var
and
vdtampere.
To
determine
the
apparent,
active
and
reactive
power of
an
inductive
load.
To improve
the
power
factor of
an
inductive
load.
We now know
the
fdlowing facts:
a)
Apparent
power
supplied
to
a
load
b
the
simple product of voltage
and
current.
b)
Active
power
supplied
to
a
load
is
measured
by
a wattmeter.
When
reactive poser
is
imrohred,
the
apparent
power
is
larger
than
the
active power.
Reactive
power
may
be
inductive
or
capaWe.
in
most
electromechanical
devices
the
reactiie power
will
be
inductive
due
to
the
inductance presented
by
coils.
Reactive power can
be
calculated
by
the
equaW
Reactive power
=
d(Apparent
power?

(Real
power2)
( 1 1
If
the
phase
angle
between
the
vottage
and
current
is
known, the active power
can
be
found
by
the
equation:
Active
power
=
E
x
1
x
cos
@
=
Apparent Power
x
cos
4
(2)
The
ratio
of
active
power
to
apparent
power
is
called
the
pawer
factor
of
an
AC
circuit.
Power
factor
can
be
found
by
the
equation:
PF =
PIE1
=
Active Power
/
Apparent Power
(3)
The
value
of
the
pawer factor
depends
on
how
much
the
current
and
voltage
are
out
of phase.
When
the
current and voltage
are
in
phase,
the
active
is
equal
to
I
x
E,
or
in
other
words,
the
power
fador
is
unity.
When
current
and
voltage
are
out
of
phase
by
90°,
as
in
a
purely
 ~ e
or
induct'i
ciradt,
the
power
factor
is
zero,
resulting
in a
zero
value
of
achral power.
In
circuits
containing
both
resistance
and
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I
Watt,
Var,
VoltAmpere,
and
Power
Factor
reactance,
the
value
of
the
power factor is
some
value
between
one and zero. If
the
phase angle
c$
between
the
voltage and current
is
known
the
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 Spring '08
 GORUR
 Power, Alternating Current, Volt, power supply, AC power, Power factor

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