122
PLZ-4WL
Operating Area
How constant power (CP) mode works
In CP mode, the PLZ-4WL sinks current so that the power consumed inside the electronic
load is constant.
Constant power mode operation
When the PLZ-4WL is used in constant power (CP) mode, it operates as a constant-power
load as shown in the figure below. When the voltage (V1) of the constant-voltage power
supply increases, the input current (I) decreases so that the power P consumed by the PLZ-
4WL is kept constant (P = V
I). In the figure below, P = V
2
I
2
= V
3
I
3
.
Transition of the operating point: overcurrent protection (OCP)
In this example, we will assume that the PLZ-4WL is being used in constant power (CP)
mode to test the load characteristic of a constant-voltage power supply.
■
Operation on segment AB
If the voltage of the constant-voltage power supply is set to V1 and the power of the PLZ-4WL
is increased (P
1
P
2
P
B
), thereby increasing the input current (load current), the operating
point moves along segment AB (A
1
A
2
B).
When point B is reached, overcurrent protection (OCP) is activated. At this point, one of two
types of operations occurs, depending on the protection action setting for OCP.
If the protection action is set to LOAD OFF, the load turns off.
If the protection action is set to LIMIT, the PLZ- 4W sinks current as a constant-current load at
point B. Even if you attempt to increase the input current, the current will not increase beyond
point B. If you decrease the input current, overcurrent protection (OCP) is cleared. The PLZ-
4WL returns to constant power (CP) mode, and the operating point moves along segment
AB.
I
V
0
The power (P) is constant even
when the current and voltage vary.
×
×
PLZ-4WL Series
Constant-voltage
power supply
V
1
Current I
Voltage
V
V
2
V
1
I
1
I
2
V
2
V
1
I
1
I
2
=
=
P
Maximum rated current
Input current [A]
Input voltage [V]
Logarithmic scale
Constant power line
(OCP setting)
Constant current line
Operating area
OCP activation point
(constant power settings: P
1
, P
2
, and P
B
)
B
V
1
V
3
G
A
H
A
1
A
2
P
1
P
2
P
B