Solid-State Switching Devices for Resistive Loads 3RF29 Function Modules Converters ■ Overview Converters for 3RF2 solid-state switching devices These modules are used to convert analog control signals, such as those output from many temperature controllers for example, into a pulse-width-modulated digital signal. The connected so- lid-state contactors and relays can therefore regulate the output of a load as a percentage. ■ Design Mounting Easy snapping onto the 3RF21/3RF22 solid-state relays or 3RF23/3RF24 solid-state contactors establishes the connections to the solid-state switching devices.
The connector on the solid- state switching devices from the control circuit can be plugged onto the converter without rewiring. ■ Function The analog value from a temperature controller is present at the 0 ... 10 V terminals. This controls the on-to-off period, as a func- tion of voltage. The period duration is predefined at one second. Conversion of the analog voltage is linear in the voltage range from 0.1 ... 9.9 V. At voltages below approx. 0.1 V the connected switching device is not activated, while at voltages above ap- prox. 9.9 V the connected switching device is always activated. 46 Siemens · 2009