Barrel Heaters - Hasmak.com.tr

W A T L O WPower ControllersSolid State Relays(SSRs)100Temperature Operating CurveAmbient Temperature—°C40 50 65 80Application HintsThermal TransferA thermal foil is provided with eachsolid state relay for mounting on thebase of the relay to improve heattransfer. In addition, two bevelwashers are supplied to provide theproper pressure for the transfer ofReplacing Contactors or MDRsImprovements in heater life andcontrol accuracy can be anticipatedwith solid state relays operated withrapid cycle times as <strong>com</strong>pared toslower operating electromechanicalrelays or even mercury displacementrelays in some applications. Whenreplacing these types of relays withthe SSR, it is important to considertwo aspects:System DiagramsShorted SSR Alarm—SDAThe most prevalent concern whenusing solid state relays is thepossibility of a relay failing in ashorted condition. With this in mind,Watlow has designed a costeffective “Shorted SSR Alarm” SDA.The device monitors the output(current through the heater) andactivates a triac (alarm) if there is noheat. Use two #8-32 screws,15.8 mm(0.625 in.) long to secure the relay tothe heatsink. See the derating curve,Temperature Operating Curve, foroperation without heatsinks.Note: This rating curve applies only to 10 and25 amp SSRs. 40 through 75 amp SSRsshould not exceed a seven amp load withoutusing a heatsink.1. HeatSolid state devices require a smallvoltage to turn on, which isconsumed as heat (1.5 watts/amp).This heat must be removed from thedevice, and is usually ac<strong>com</strong>plishedby mounting the relay on heatsinks.2. Failure ModeSolid state devices should last formany years when properly protectedwith voltage and RC suppressors<strong>com</strong>mand signal from thetemperature controller.The triac can be wired to a bell, orto a normally closed latching relayto remove power to the heater.L1L2Percent of Rated Current80604020With HeatsinkIn Free Air075 100 125 150 175 200Ambient Temperature—°Fmounted on appropriate heatsinks,and when fused against the highcurrents caused by electrical shorts.However, if the unit fails, the mostprobable condition will be a short.Both mechanical relays mentionedabove also have a good probabilityof failing short. In all cases whereuncontrolled full power can causedamage, it is re<strong>com</strong>mended that ahigh limit temperature controller andcontactor be used for protection.Single-Phase—SDATempControlOpenCollectorContactorSolidStateRelayD.C.- +Thermocouple0 and5VÎ(dc)on-offRelayHeaterMountedCurrentTransformerSDAShorted SSRDetectorSingle-Phase—SBL4-20mA loop powered firing card fordirect mounting on a dc solid staterelay. Can be used in three-phasemode with two dc input solid staterelays.Single-Phase—AT and BTRequires external power switchingtransformer. Consult factory for partnumber and voltage required.SSRCodeCard Description No.SBL Burst firing 4-20mA only 08-5399loop powered cardfor dc input relays onlySDA Shorted SSR alarm 08-5386for dc input relays onlyAT Single-phase, phase- 08-5422angle firingBT Single-phase variable 08-5406time base, single cycle,burst firing transformerpower. 4-20mA inputL1L2TempControl4-20mAÎ(dc)OutputFuseWith Loop Powered BoardSBL+ -DCSSRHeater359