Solid State Relays

More For Less: Longer Heater Life at Lower Cost

Watlow solid state relays (SSR) offer many of the advantages of solid state power controllers, but at a lower cost. Watlow's extensive knowledge in power controller design led to the development of a special fast cycle input card that enables a solid state relay to operate from a standard 4-20mA instrumentation command signal. Test results show that zero-cross solid state relays in combination with the fast cycle card promote better temperature control and longer heater life than slow cycle relays. Through a time proportional cycle rate of 1⁄10 of a second, heater life will be extended.

Both low and high voltage solid state relays are available from 24 to 660VAC. All ac output models include back-to-back silicon controlled rectifiers (SCRs) for a more rugged design than the traditional triac-based solid state relay. The internal design allows it to tolerate high currents and harsh electrical environments of heavy industry. Watlow also offers a switched VDC model for dc heating applications.

Watlow provides all of the components necessary for trouble-free operation. This includes two standard convenience items: a thermal foil to ensure proper thermal transfer from the relay to the heat sink and belleville washers to ensure that the relay is mounted with sufficient pressure to enable good heat transfer. Matched semiconductor fuses and heat sinks are available to complete the power switching package.

Features & Benefits

Fast cycle card increases heater life, optimizes temperature control and accommodates higher watt density heaters

Zero cross firing for minimal electrical noise

Back-to-back SCR design withstands harsh or hostile industrial environments

Meets applications requiring agency approval


Description Information
Mounting Back panel
Profiling No
Max Output 75A
Output Firing Zero Cross
Phase Configurations 1
Ambient Operating Range 25 to 85°C (77 to 185°F)
Agency Approvals UL®, CSA, SCCR
TRU-TUNE®+ Adaptive Control No
Remote Limit Reset No
Warranty (Years) 2

Related Documentation

  • User Manuals

    Cross Reference for Semiconductor Fuses and Holders for Watlow Power Controllers

    SBL Card Data Sheet

    SDA Card Shorted Solid State Relay Detector Data Sheet

    Solid State Relay (SSR) Mounting and Installation Instructions

    VPAC Solid State Relay Power Control User's Manual

    VPAC-AT Remote Mount Transformer Data Sheet

    VPAC-BT Remote Mount Transformer Data Sheet

  • Agency Approvals

    Agency Approvals for Watlow Controllers

    CCC Winona Exemption Letter

  • Brochures

    SCR Power Controllers

  • CAD Drawings

    Solid State Relay 2D files in AutoCAD 2000

    Solid State Relay files in CorelDRAW x5

    Solid State Relay files in PDF

  • Training and Education

    Variable Time Base Zero Cross Function - Oscilloscope Video

  • Catalogs

    Controller Catalog (Section) - Power Switching Devices

    Sensor & Controller Catalog

  • Specification Sheets

    Solid State Relay

    Combined Branch Protection and Semiconductor Fusing

    DIN-RAIL Semiconductor Fusing

  • White Papers

    SCCR - Short Circuit Current Rating for Watlow Power Controls

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Quality Certificates

ISO 90012008 Certificate - Controllers Winona