W A T L O W
Application Guide
Power Controllers
The discrete output device that acts in response to a deliberate guidancefrom the temperature controller is thepower controller.There are four common power con-trollers: electromechanical relays,
mercury displacement relays, solidstate relays and silicon controlledrectifiers (SCRs). The first two usemagnetic devices to actuate powerswitching. The latter two use solidstate electronics to effect the switching
function. The selection of a specific
power controller type depends onthemethod of control being used,system power demands, degree oftemperature control (accuracy to set
point), the heater type and heater liferequirements.Watlow manufactures a wide range of mercury displacement relays, solidstate relays and SCR power control-lers in ratings to meet almost all power
Industrial temperature controllers Product Overview
Power Controllers Watlow solid state power controllers complement the rapid switching requiredby PID temperature controllers and help deliver optimum system performanceand service life. Available in 1-phase and 3-phase/2-leg and 3-leg configur-
ations, Watlow power controllers meet most
industrial heating applications.Random, zero cross or phase angle fire options match the power controller to
the application requirement. DIN-A-MITE SCR power controllers provide a
convenient DIN rail mount package in current ratings from 18 to 100 amperes –
a good replacement for equal mercury displacement relays. Qpac SCR powercontrollers rated up to 1,000 amperes for those large process heatingapplications. POWER SERIES microprocessor based SCR power controllerswith ratings from 65 to 250 amperes. The POWER SERIES offers extensivesystem and heater diagnostics features and agency approvals. SERIES CZR is
a CSA, VDE and UL
® recognized contactor with ratings from 18 to 50 amperessingle phase. Single
solid state relays from 10 to 75 amperes. E-SAFE
® relay isa 3-pole hybrid solid state/mechanical relay with current ratings of 20 and 40amperes and is UL
® -508 listed and C-UL
® . E-SAFE is a good mercurydisplacement relay replacement in the amperages it serves.
switching needs. Each is manufac-tured to the highest standards of
reliability and performance. For more
information specific to powercontroller types, models and ratings,see the “Power Controllers” productsection of Watlow’s Temperature and
Power Controller’s catalog, page 121. 101