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.A characteristic 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-EffectTransistor.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.

Triac - 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

Questions? Call or e-mail

+1 (877) 502 5500

+44 (0) 1202 606030

sales@crydom.com

sales-europe@crydom.com

Americas

Europe

18

32

24

16

8

6

4

0.6" Modules

M Series

SM Series

C4 Series

Quads

Number of Modules

Mounting boards available