Frequently Asked Questions:

Frequently Asked Questions:

Component Schematics

Specifying an SSR Terminologies

Typical Applications for Solid State Relays

What is an SSR?Why use an SSR?

What are the part numbers for the Dual and Quad relays 4 pin header connectors?

Mean Time Between Failures (MTBF) of Crydom Products

 

Component Schematics

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Specifying an SSR

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Consideration must be given to:

  • Load Voltage - AC or DC, Line Voltage.
  • Load Current - AC or DC, Max and Min.
  • Input Voltage - AC or DC, Max and Min.
  • Ambient Temperature - Required for Derating and heatsink calculations.
  • Mounting Style - PCB, Chassis or DIN Rail Mounting
  • International Approvals - UL, CSA, VDE, TUV, etc.



Terminologies

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SCR A semiconductor which is made from silicon used to convert AC power to DC which can be used to control or rectify AC power semiconductors.
Diode A semiconductor which allows electric current to flow easily in one direction but not in the other.
Rectifier A semiconductor used to convert AC power to DC. It allows current to flow in one direction and prevents the flow of current in the opposite direction.
Discrete Device An individual electrical component packaged or unpackaged, such as a resistor, capacitor, transistor, diode, etc.
Heat sink A material with good heat conducting or dissipating properties to which a packaged device is attached to cool and maintain the output semiconductor junctions within the rated temperature range.
Trigger To turn on an SCR utilizing its gate.
Thyristor A term for the general class of semiconductor devices which includes SCR’s, triacs, alternistors, etc.
Anode Positive terminal of an SCR or Diode. Positive with respect to cathode and or gate terminals.
Cathode Negative terminal of an SCR or Diode with respect to the anode.



Typical Applications for Solid State Relays

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All motors need some form of switching for control. SSRs offer a high reliability alternative to electro-mechanical contactors.

Switching solenoids
Issuing of product
Issuing of cups
Issuing of liquids

Controlling Heaters
Commercial Coffee Machines
Commercial / Industrial Cooking Equipment
Plastics Industry (extrusion / thermoforming)
Plastics Industry (drying)
Packaging Industry
Heat Tracing
Industrial Cleaning Equipment
Solder Wave / Reflow Systems

HVAC&R
Compressor Control
Blower Control
Motorized Duct / Vent Control
Anti-Condensation Equipment

Lighting Control Systems
Dramatic Theatrical Effects
Mobile Stage Shows
Traffic Signal Systems
Motorway Information Systems
Lifts & Escalators
Automatic Door Operation

High Reliability
Medical Equipment
Low Switching Noise
Low Electromagnetic Interference



What is an SSR?

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  • A totally electronic device that depends on the electrical, magnetic, and optical properties of semiconductors to control the flow of current in a circuit.
  • An alternative to Electro-mechanical relay offering enhanced electrical performance and reliability.
  • A switch that has no moving mechanical parts - Solid State



Why use an SSR?

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  • Extremely Long Life
  • Silent Operation
  • No Moving Parts Eliminates Arcing & Switch Bounce
  • Resistant to Shock and Vibration
  • Reliable Operation in Harsh Environments
  • Operation is Not Dependent Upon Orientation
  • Low Power Consumption
  • Reduced Electromagnetic Interference



What are the part numbers for the Dual and Quad relays 4 pin header connectors?

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Suggestions for the 4 pin header connections on the Dual and Quad SSR’s with .025” square input pins:

Amp: 640440-4, (22 Awg); 640441-4, (24 Awg); 640442-4, (26 Awg)

Molex: 14-60-0043; 14-60-0041; 14-56-6049; (for Awg 26, 24, and 22 respectively) These Molex parts come with the sockets pre-loaded.



Mean Time Between Failures (MTBF) of Crydom Products

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Calculating Mean Time Before Failure (MTBF) for a solid-state relay is, at best, a tricky proposition. Unlike a typical electromechanical relay, there are several variables that will directly impact the life expectancy of a solid-state relay in a given application. These variables primarily revolve around the electrical characteristics of the application, such as load current, the duty-cycle of the load, the ambient temperature inside the panel, surge currents, etc. However, mechanical issues such as the mounting method, available airflow, and thermal interface between the relay and the panel / heat sink also impact the relay’s life expectancy.

Therefore, Crydom does not publish a “fixed” MTBF specification. Instead, we provide an estimated MTBF specification range based on historical observation. That is, we calculate the MTBF by taking the total in-service hours over the previous two-year period and dividing that by the number of returns we have received from the field over the same period of time (solid-state relays that were misapplied by the customer are not considered in the calculation). “In-service hours” is simply calculated by taking the number of products shipped over the specified period and assuming that they were in operation for eight hours per day over a five day work week. Then, to ensure that we maintain an adequate margin of error, we assume that only 10% of all field failures are returned to us for analysis and adjust the results accordingly.

The final result yields a MTBF rating of between 2 million and 40 million hours, depending upon the product family. However, for the sake of simplicity we state that the MTBF rating for our solid-state relays is >2 million hours with a quality level of approxim


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