Datasheet

Solid State Relays Common Precautions
■Actual Operation
1. Leakage Current
A leakage current flows through a snubber circuit in the SSR
e
ven when there is no input. Therefore, always turn OFF the
input or load and check that it is safe before replacing or wiri
ng
th
e SSR.
2. Cutting Terminals
Do not cut the terminals using an automated-cutter. Cutting the
terminals with devices such as an automated-cutter ma
y
dama
ge the internal components.
3. Deformed Terminals
Do not attempt to repair or use a terminal that has been
deformed. Otherwise excessive force will be applied to the SSR,
and it will lose its original performance capabilities.
4. Hold-down Clips
Exercise care when pulling or inserting the hold-down clips so
that their form is not distorted. Do not use a clip that has already
bee
n deformed. Otherwise excessive force will be applied to t
he
SSR, ca
using it not to perform to its specification, and also it will
not have enough holding power, causing the SSR to be loose,
and resulting in damage to the contacts.
5. PCB SSR Soldering
x SSRs must be soldered at 260°C within five seconds. For
mod
els, however, that conform to separate conditions, perform
soldering according to the specified requirements.
x Use a rosin-based non-corrosive flux that is compatible with
the material of the SSR.
6. Ultrasonic Cleaning
Do not perform ultrasonic cleaning. Performing ultrasonic
cl
eaning after the SSR base has been installed will cause
ultrasonic waves to resonate throughout the SSR internal
structure, thereby damaging the internal components.
■Safety Concept
1. Error Mode
The SSR is an optimum relay for high-frequency switching and
highspeed switching, but misuse or mishandling of the SSR ma
y
da
mage the elements and cause other problems. Th
e SSR
con
sists of semiconductor elements, and will break down if thes
e
el
ements are damaged by surge voltage or overcurrent. Most
faults associated with the elements are short-circuit
malfunctions, whereby the load cannot be turned OFF.
Therefore, to provide a safety feature for a control circuit using
an
SSR,
design a circuit in which a contactor or circuit breaker on
the load power supply side will turn OFF the load when the
SSR
cau
ses an error. Do not design a circuit that turns OFF the l
oad
po
wer supply only with the SSR. For example, if the SSR caus
es
a hal
f-wave error in a circuit in which an AC motor is connected
as a load, DC energizing may cause overcurrent to flow through
the motor, thus burning the motor. To prevent this from occurring,
design a circuit in which a circuit breaker stops overcurrent to the
mot
or.
2. Short-circuit Protection
A short-circuit current or an overcurrent flowing through the load
of
the SSR will damage the output element of the SSR. Connect
a quick-break
fuse in series with the load as a short-circuit
protection measure.
Design a circuit so that the protection coordination conditions f
or
t
he quick-break fuse satisfy the relationship between th
e SSR
surg
e resistance (I
S), quick-break fuse current-limiting feature
(I
F), and the load inrush current (IL), shown in the following chart.
3. Operation Indicator
The operation indicator turns ON when current flows through the
input circuit. It does not indicate that the output element is ON.
Switch element Snubber circuit
Varistor
Trigger circuit
Input circuit
Leakage
current
Location Cause Result
Input area Overvoltage Input element damage
Output area
Overvoltage
Output element damage
Overcurrent
Whole Unit
Ambient temperature
exceeding maximum
Output element damage
Poor heat radiation
IS
IF
IL
IS>IF>IL
Time (ms)
Peak current (A)
Input terminal
Input circuit
Output circuit
Output terminal
Input indicator
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