Glossary of Terms
Terminology
Control Voltage Range - the range of voltage when applied across the SSR Input terminals,
will maintain an ON condition across the Output terminals.
Control Current - Current drain on the control source at specified SSR input voltages and
On/Off conditions.
dv/dt -Maximum rate of rise of voltage applied across the output terminals that the SSR can
withstand without turning ON.Acharacteristic of thyristors used in AC SSRs.
dv/dt Off State (Static) - Specified as a minimum dv/dt withstand capability of SSRs in the
off or blocking state.
Form, Contact -
Contact or output configuration, as in Form A for Single Pole, Single Throw,
Normally Open (SPST-NO)
Holding Current - The minimum load current required to maintain a thyristor in its
conducting state.
Input Current (Maximum) - Current drain on the control source at specified SSR input
voltages and On/Off conditions.
Isolation Voltage - The value of dielectric strength measured between the input and output,
input to base, or output to base.
LED - Light Emitting Diode, commonly used for status indication on some models of SSRs
and as the light source in a photocoupler .
Line Voltage Range - The range of voltages applied to the output, over which the SSR will
continuously block or switch and otherwise perform as specified.
Load Current Range - The range of current applied to the output, over which the SSR will
continuously block or switch and otherwise perform as specified.
MOSFET - Metal Oxide Semiconductor Field-Effect Transistor.The control electrode (gate) is
generally isolated from the source electrode by a layer of silicon oxide. A voltage applied
between the gate and the source will provide a current flow between the drain and the source.
Normally Open (NO) - A contact or SSR output that is open when no control power is
present at the input (coil).This is a Form A device.
Normally Closed (NC) - A contact or SSR output that is closed when no control power is
present at the input (coil).This is a Form B device.
Off-State Voltage - The maximum transient voltage that an SSR output can withstand
without malfunction or damage.
On-State Voltage (Maximum) - The peak voltage that appears across the SSR output
terminals at full rated load current.
Phase Control -
Turn-On of a non-zero switching SSR (each half cycle), at a phase angle
determined by the control signal source.
Photocoupler/Isolator - A combination of light-emitting diode and light-sensitive
semiconductor used to transmit information optically while providing electrical isolation.
Commonly used isolating element for coupling the control signal to the output in an SSR.
Power Dissipation - The maximum average power dissipation (Watts) resulting from the
effective voltage drop (power loss) in the SSR output semiconductor.
Rectifier - Asemiconductor used to convert AC power to DC.It allows current to flow in one
direction (forward) and prevents the flow of current in the opposite directions (reverse).
SCR - Silicon Controlled Rectifier. Unidirectional semiconductor of the thyristor family with
latching properties.
Snubber - A resistor-capacitor combination placed across the SSR output terminals to
reduce dv/dt and transients in thyristor circuits.
Solid State Relay (SSR) - Isolated On-Off switch composed of non-moving electrical parts
(primarily semiconductors, transformers and passive components).
Surge Current - The maximum allowable SSR momentary current flow for a specific time
duration.Typically specified as a peak value for one line cycle for AC.
Thermal Resistance - Expressed in degrees Celsius per watt (˚C/W).This value defines the
temperature gradient in the path between the power generated in the output SSR
semiconductor and the final dissipating medium (heat sink/air).
Thyristor - A semiconductor bistable device comprising three or more junctions (PNPN,
etc).The generic name for a family of gate controlled switches including SCRs and triacs.
Tr i a c - Bidirectional semiconductor of the thyristor family. Performance is similar to that of
an inverse pair of SCRs, triggered by a single gate electrode.
Trigger - To turn on an SCR or triac.
Turn-Off Voltage (Must Release) - The voltage applied to the SSR input at or below which
the output must be in the Off-State (Normally-Open).
Turn-On Voltage (Must Operate) - The voltage applied to the SSR input at or above which
the output must be in the on state (Normally-Open).
Crydom offers a broad line of digital I/O modules and mounting
boards. Designed for long, reliable service in demanding industrial
environments, these modules provide optical isolation between
logic-level control systems and external loads, such as motors,
valves, solenoids, resistive heating elements, etc.. Output modules
within the offer can switch loads up to 5 Amps at 24-280 VAC (Form
A, SPST-NO, zero-crossing output), or up to 5A/3A at 100/200 VDC
(Form A SPST-NO). Input modules provide digital feedback to the
control system when the load is energized and are available with
inputs up to 280Vac / 48 VDC, with either a 5 VDC or 24 VDC logic-
level output.
0.6" Modules
AC Inputs for 24 V, 120 V, 240 V
DC Inputs for 3.3 to 32 V, 10 to 48 V
4 kV Optical Isolation
Plugs into 0.6" Mounting boards
M Series
AC Inputs for 24 V, 120 V, 240 V
DC Inputs for 3.3 to 32 V, 10 to 48 V
4 kV Optical Isolation
Plugs into M Series Mounting boards
SM Series
AC Inputs for 24 V, 120 V, 240 V
DC Inputs for 3.3 to 32 V, 10 to 48 V
4 kV Optical Isolation
Plugs into SM Series Mounting boards
C4 Series
Built-in LED Status Indicator
Regulated Supply Voltage
4 kV Optical Isolation
Replaceable 2 AG Type Fuse (output modules)
Plugs into C4 Series Mounting boards
I/O Modules
Industry Standard Packaging
UL Recognized, CSA Certified,
CE Compliant
Quads
4 Input Circuits per module
AC Inputs for 24 V, 120 V, and 240 V
DC Inputs for 4 to 32 V, 10 to 60 V
4kV Optical Isolation
Plugs into mounting boards for quad-pack modules
I/O Modules
Questions? Call or e-mail
+1 (877) 502 5500
+44 (0) 1202 606030
sales@crydom.com
sales-europe@crydom.com
Americas
Europe
18
32241686
4
0.6" Modules
M Series
SM Series
C4 Series
Quads
Number of Modules
Mounting boards available
