Publication 700-AT001A-EN-E June 2002
Basic Concepts of SSRs
1-7
SSR Glossary
Terms
Meaning
Insulation
Basic insulation
Insulation for basic protection from electric shock
(IEC950 1.2.9.2)
Supplemental
insulation
Independent insulation provided outside of basic
insulation to protect from electric shock when the
basic insulation breaks down (IEC950 1.2.9.3)
Reinforced
insulation
A single-layer of insulation (IEC950 1.2.9.5) that
provides the same protection from electric shock as
double insulation (insulation including both basic and
supplemental insulation) according to conditions
stipulated in IEC950 standards
Circuit
functions
Zero cross circuit A circuit which starts operation with the AC load
voltage at close to zero-phase.
Trigger circuit
A circuit for controlling the triac or thyristor trigger
signal, which turns the load current ON and OFF.
Input
Isolated input
circuit
If the external circuit is prone to generating noise, or
if wires from external sources are prone to the
influence of inductive noise, in order to prevent
malfunctions due to noise, it is necessary to
electrically isolate internal circuits and external
circuits (output circuits). An isolated input circuit is a
circuit that isolates inputs and outputs by using
components that are not connected electrically but
that can transmit signals, such as contact relays or
photocouplers.
Photocoupler
A component that runs the electric signal into a light
emitter (e.g., LED), changes it to a light signal, and
then returns it to an electric signal using a
photoelectric conversion element, such as a photo
transistor. The space used for transferring the light
signal is isolated thus providing good insulation and
a high propagation speed.
Rated voltage
The voltage that serves as the standard value of an
input signal voltage
Must-operate
voltage
Minimum input voltage when the output status
changes from OFF to ON.
Input impedance The impedance of the input circuit and the resistance
of current-limiting resistors used. Impedance varies
with the input signal voltage in case of the constant
current input method.
Operating
voltage
The permissible voltage range within which the
voltage of an input signal voltage may fluctuate.
Reset voltage
Maximum input voltage when the output status
changes from ON to OFF.
Input current
The current value when the rated voltage is applied.
