Kikusui PBZ20-20, User Manual

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6
PBZ
Unipolar power supplies
(First- and third-quadrant operation)
The voltage polarity of general power supplies is fixed to a
single polarity; thus they are called unipolar power supplies. If
voltage is applied to a resistive load from a unipolar power
supply, current that is proportional to the voltage flows in a
fixed direction. The current flows from the output voltage’s
positive terminal to the output voltage’s negative terminal. This
is positive current. If you change the polarity of the voltage, the
current flows in the opposite direction. This is negative current.
The operation of a unipolar power supply is shown on a graph
of voltage (vertical axis) versus current (horizontal axis). First-
quadrant operation is where positive current flows, and third-
quadrant operation is where negative current flows.
The following figures show examples of the operation of
unipolar power supplies. The points on each waveform (a, b,
c, d, f, and g) are used to indicate the relative time relationship
between the voltage and current waveforms. The
corresponding points on each waveform indicate the same
time positions relative to t0. This holds true for the following
sections as well. These examples show that the voltage and
current are in phase.
Bipolar power supplies
Unlike with resistive loads, when a power supply that
alternates voltage polarity based on time is applied to an
inductive or capacitive load, the current phase becomes
lagging or leading to the voltage phase.
If this occurs, there are four possible combinations of the
voltage and current polarities. This operation is shown on a
graph of voltage (vertical axis) versus current (horizontal axis).
The PBZ operates in all four quadrants (and thus the name
four-quadrant operation). Power supplies that can operate in
this manner are called bipolar power supplies.
The following figures show examples of four-quadrant
operation. These examples show that the current phase
becomes lagging to the voltage phase. The waveform passes
through all four quadrants and creates an ellipse.
Section ab is in the second quadrant; section bcd is in the first
quadrant; section df is in the fourth quadrant; and section fga
is in the third quadrant. As the waveform continues, it
repeatedly moves through all four quadrants.
Unipolar and bipolar power supplies
t
0
t
1
t
2
t
3
t
4
t
0
t
1
t
2
t
3
t
4
V
-V
V
I
-I
I
a
b
c
d
f
g
a
b
c
d
f
g
a
b
c
d
f
g
First quadrant (positive)
Third quadrant (negative)
t
0
t
1
t
2
t
3
t
4
t
0
t
1
t
2
t
3
t
4
V
-V
-V
I
-I
-I
a
b
c
d
f
g
a
b
c
d
f
g
a
b
c
d
f
g
2 1
3 4
Power
Voltage
Current
+
-
+
-
Power waveform
t
0
t
1
t
2
t
3
t
4
t
0
t
1
t
2
t
3
t
4
t
0
t
1
t
2
t
3
t
4
V
-V
V
-V
I
-I
I
-I
a
b
c
d
f
g
a
b
c
d
f
g
a
b
c
d
f
g
a b c d f g
Third quadrant
Fourth quadrant
First quadrant Second quadrant