FAQ No. FAQ01913
Question
What is overload protection function?
Answer
The overload protection function prevents
damage to the Power Supply and load from an overload (including an
overload due to a shorted output).
When a current greater than the overcurrent detection value (actual value
depends on the Power Supply being used) is detected, the protection
function will operate and the output current will be limited. In addition,
the output voltage will also drop in accordance with the load's status,
i.e., the load's impedance. The level to which the voltage drops depends
on the overload status and the impedance of the load wiring.
The output voltage drop characteristics can be divided into the three
following categories.
|
Drop characteristics |
Voltage vs. current curve |
Trend |
|
Inward-sloping drop |
|
The output current tends to drop as the output voltage
drops. |
|
Straight drop (Inverted L drop) |
|
The output current remains fairly constant as the
output voltage drops. |
|
Outward-sloping drop |
|
The output current tends to rise as the output voltage
drops. |
These curves are called drop curves and basically the output is
continuous during the drop. When the overcurrent condition is eliminated,
the output will return to normal automatically (automatic reset).
The following characteristics may occur together with the three drop
characteristics shown in the table above.
|
Output |
Voltage vs. current curve |
Trend |
|
Intermittent operation |
|
The output becomes intermittent if the voltage drops
below a certain level. The Power Supply itself reduces its load by
making the output intermittent. |
|
Interrupted
operation |
|
The output is stopped if the overload condition lasts
longer than a preset time. The Power Supply itself has no load because
the output is stopped. |
These drop characteristics can also be referenced as the maximum output
current that can be supplied to a load when the power is turned ON (during
the output voltage startup process).
When selecting a Power Supply for a load that starts from a low voltage
(such as a load with a built-in DC-DC converter) or a capacitive load that
absorbs a significant inrush current, consider the Power Supply's overload
protection characteristics and the load's startup characteristics.
Typically, the Inverted L drop characteristic is the most suitable.
Main drop characteristics (for reference)
| Inward-sloping drop |
S82K (3 W, 7.5 W, 15 W) |
| Inverted L drop (Straight
drop) |
S82J (100 W (5 V, 12 V, 15
V), 150W), S82K (90 W, 100
W, 240 W), S8TS |
| Inward-sloping drop with
intermittent operation |
S82J (10 W, 25 W) |
| Inverted L drop with
intermittent operation |
S8PS (300W),
S8VS |
| Outward-sloping drop with
intermittent operation |
S82J
(50 W, 100 W (24 V)),
S82K
(30 W, 50 W), S8PS (50 W, 100 W, 150 W) |
| Inverted L drop with
interrupted operation |
S82J
(600 W), S8PS (600 W) |
Note:
1. If the S82J is connected to a load with a built-in DC-DC converter (a
electronic device such as a PLC or digital multimeter) or a capacitive
load, the overload protection function may be triggered at startup and the
Power Supply may not produce an output.
2. Do not continue using the Power Supply with an overcurrent or with the
output terminals short-circuited. Doing so may shorten the service life of
internal components or may cause them to fail entirely.
3. Even if the load is short-circuited, the drop in voltage will vary
depending on factors such as the impedance in the load line.
4. Even if different models have the same drop characteristics, the actual
characteristics (output current, output voltage, etc.) will vary from
model to model.
5. Additional precautions apply to some models.
Applicable Models: All Models
Other Power Supply
FAQs
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