MDRs

Mercury displacement relays (MDRs) switch power either ON or OFF by applying AC or DC control voltage to the solenoid. This action causes a plunger to raise and lower the mercury level, and make or break the power circuit. The MDR is capable of switching 25, 30 and 50 amps per pole at up to 480VAC. Watlow offers three MDR styles which all come in 1-, 2- or 3-pole versions MDRs provide a long life alternative to contactors and electromechanical relays and are well suited for applications sensitive to current leakage. MDRs are position sensitive and must remain upright at all times. MDRs are not well suited for applications requiring rapid switching cycles, like PID temperature control. Applications Plastic injection molding machines Wave soldering

Solid State

SSR Well suited to provide the rapid switching cycles required by PID temperature control, solid state relays (SSRs) can switch from 10 to 75 amps up to 480VAC. Switching can be either zero cross from AC or DC input voltages, or random from DC input voltage. SSRs must be used with a correctly sized heatsink to assure proper service life. SSRs leak current in the off-state. Applications Food processing Lighting equipment

SCR Capable of zero cross or phase angle operation, or burst firing to act as a solid state contactor, SCRs offer power switching advantages not possible with MDRs or SSRs. Available in ratings from 10 to 1000 amps, up to 575VAC, in 1-phase, 3-phase/2-leg and 3-phase/3-leg versions. Zero cross variable time base extends heater life and permits more accurate control. Phase angle firing permits "soft starting" loads that change resistance over time and temperature (silicon carbide and tungsten heaters). The SCR replaces more expensive and harder-to-control saturable core transformers. Applications Heat treating Drying ovens Plastics extrusion Petrochemical

DIN-A-MITE® An ideal replacement for mercury displacement relays, the DIN-A-MITE features the same footprint as many comparably rated MDRs. Four styles meet most power switching needs, including CE compliant models, and are available in ratings from 24 to 100 amps, up to 600VAC, in 1-phase, 3-phase/2-leg and 3-phase/3-leg versions. Switching modes include zero cross and solid state contactor. Selected models offer phase angle firing. Touch-safe exterior, and DIN or sub-panel mounting make DIN-A-MITE easy and fast to install. No need to specify an SSR, heatsink and wiring--it's all in one convenient package. Applications Glass processing Ovens/furnaces Wave solder and reflow Packaging foodservice equipment Semiconductor processing