Omron S82J Series Technical Information Download Page 3

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Power Supply

Technical Information

Power

supp

lies

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Internal Fuse

If the internal fuse has blown, it is very likely that internal circuits
of the Power Supply have been damaged and that parts other
than the fuse will also need to be replaced. If the fuse has blown,
consult your OMRON representative.
If the fuse has blown, short-circuit current will not continue to
flow on the primary side (i.e., the external side) of the Power
Supply. There is, however, no protection function for the input
power lines.

●

Inrush Current

When a Switch-mode Power Supply is turned on, a surge of
current flows into the input smoothing capacitor to charge the
capacitor. This current surge is called the “inrush current.” The
inrush current varies depending on the application timing and the
presence of an inrush current protection circuit, but is usually
several to several tens of times greater than the steady-state
input current.

When two or more Switch-mode Power Supplies are connected
to the same input, the total current is the sum of the currents for
each Power Supply. Therefore, check the fusing characteristics
of fuses and operating characteristics of breakers making sure
that the external fuses will not burn out and the circuit breakers
will not be activated by the inrush current. The inrush current
pulse width can be considered to be about 5 ms. (Refer to the
following diagram.)
In particular, models with 100-to-240 VAC input have higher
inrush current energy than models with single rated inputs or
models with switching inputs. Therefore, consider the
coordination with the breaker.
The following table provides guidelines for fuse and breaker
selection.

Note. The duration of the inrush current is 5 ms max. Therefore, the fusing

characteristics require the inrush current to flow sufficiently for up to 5 ms.

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Leakage Current

Switch-mode Power Supplies have an internal noise filter circuit
that prevents switching noise from being fed back to the input
lines and protects the internal circuit from external noise.
Leakage current is largely due to the current that flows through
the capacitors (C

or C

) of the input filter circuit.

Depending on the Power Supply’s configuration, leakage current
can be reduced by incorporating an internal filter circuit.

The ACG terminal on the S82W Power Supply, which is
connected between capacitors C

and C

of the filter circuit, is

short-circuited to the

terminal by the short bar. Leakage

current can be reduced by removing the short bar.
When the leakage current poses a problem, such as when using
more than one Power Supply, remove the short bar from each
Power Supply.

To prevent electric shock, however, be sure to ground
the

terminal.

In this case, however, the input filter cannot function effectively,
resulting in greater
output ripple noise
and feedback noise.
To suppress this
noise, connect an
external noise filter
circuit as shown
below.

Leakage current cannot be reduced in Power Supplies
without an ACG terminal due to the filter circuit
configuration.

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Ripple and Noise

Since Switch-mode Power Supplies operate at high frequencies
(i.e., as high as 20 kHz or more), the DC output will contain ripple
and noise. The following figure shows a representative waveform
for ripple and noise.

Since ripple and noise contain high-frequency components, the
ground line of the oscilloscope must be shortened when making
measurements. If the ground line is too long, it acts as an
antenna which is influenced by radian waves and, consequently,
the correct values of ripple and noise cannot be measured.

●

Voltage Adjustment Range

The range over which the output voltage can be adjusted while
maintaining specific output characteristics.

Note 1. The output voltage can effectively be converted to a value above the

specified range. When adjusting the voltage, however, check the actual
output voltage and make sure it is within the specified output voltage
range.

Note 2. Make sure that the output voltage

output current does not exceed the

rated output capacity and that the output current does not exceed the
rated output current.

Note 3. Do not apply unnecessarily strong force to the Output Voltage Adjuster

(V.ADJ). Doing so may damage the V.ADJ.

Selection points

External fuses