120
PLZ-4WL
Operating Area
■
Operation on segment CD
If the voltage of the constant-voltage power supply is set to V2 and the input current (load
current) of the PLZ-4WL is increased, the operating point moves along segment CD. Point D
is the maximum current in the range being used.
How constant resistance (CR) mode works
In constant resistance (CR) mode, the PLZ-4WL sinks current in proportion to the voltage
variation.
Constant resistance mode operation
When the PLZ-4WL is used in constant resistance (CR) mode, it operates as a resistive load
as shown in the figure below. When the voltage (V1) of the constant-voltage power supply
varies, the PLZ-4WL sinks current to maintain I = V/R, with the specified resistance R fixed.
This mode cannot be used with an AC circuit.
Transition of the operating point: overpower protection (OPP)
In this example, we will assume that the PLZ-4WL is being used in constant resistance (CR)
mode to test the load characteristic of a constant-voltage power supply.
If the overcurrent protection (OCP) setting I
OCP
is greater than the current value IB at point B,
when the PLZ-4WL resistance is decreased (R
1
R
2
R
B
) so that the input current (load
current) increases, with the voltage of the constant-voltage power supply at V1, the operating
point moves along segment AB (A
1
A
2
B). When point B is reached, overpower protection
(OPP) is activated.
At this point, one of two types of operations occurs, depending on the protection action
setting for OPP.
If the protection action is set to LOAD OFF, the load turns off.
I
V
PLZ-4WL Series
Constant-voltage
power supply
The resistance (R) is constant even
when the voltage and current vary.
0
V1
Current I
Voltage
V
V
2
V
1
I
1
I
2
V
2
V
1
I
1
I
2
=
=
R
Input current [A]
Input voltage [V]
Logarithmic scale
V1
A
B
(OPP setting)
Constant power line
Operating area
OPP activation point
Constant resistance line
I
B
I
OCP
A
1
A
2
R
1
R
2
R
B
(constant resistance settings: R
1
, R
2
, and R
B
)
