Solid-State Switching Devices for Resistive Loads 3RF29 Function Modules Power controllers ■ Overview If the left potentiometer t R is set to greater than 0 s, then the power controller operates according to the principle of genera- lized phase control. Generalized phase control Power controllers for 3RF2 single-phase solid-state switching devices The power controller is a function module for the autonomous power control of complex heating systems and inductive loads, for the operation of loads with temperature-dependent resistors and for simple indirect control of temperature.
In order to observe the limit values of the conducted interference voltage for industrial networks, the load circuit must include a re- actor with a rating of at least 200 µH. The power controller can be used on the instantaneously swit- ching 3RF21 and 3RF23 solid-state switching devices (single- phase). If only the full-wave operating mode is used, the power controller can also be used on the "zero-point switching" solid- state relays and contactors. For SIDAC reactors for generalized phase control mode see page 50. Setpoint selection The setpoint selection is set either internally with the right-hand potentiometer P to 0 ... 100 % on the module or externally using the analog input 0 ...
10 V. The following functions have been integrated: • Power controller for adjusting the power of the connected load. Here, the setpoint value is set with a rotary knob on the module as a percentage with reference to the 100 % power stored as a setpoint value. • Inrush current limitation: With the aid of an adjustable voltage ramp, the inrush current is limited by means of phase control. This is useful above all with loads such as lamps or infrared lamps which have an inrush transient current. • Load circuit monitoring for detecting load failure, partial load faults, alloyed power semiconductors, lack of voltage or a break in the load circuit.
In the case of full-wave control, 100 % corresponds to continuo- usly On and, in the case of generalized phase control, to a con- duction angle of 180° – and therefore maximum output. 180° 100 Conduction angle Modulation % 90° 50 Special versions 3RF29 04-0KA13-0KC0 NSB0_01693 During the Teaching process the connected solid-state relay or contactor is not activated; i. e. no current flow takes place. No current reference value is stored. No part-load monitoring! 0° 0 5,0 V External setpoint of analog voltage 0 ... 10 V > 9,9 3RF29 ..-0KA1.-0KT0 No part-load monitoring!
100 0 50 % Internal setpoint of potentiometer P ■ Design Mounting Input characteristic Internal setpoint selection Easy snapping onto the 3RF21 solid-state relays or 3RF23 solid- state contactors establishes the connections to the solid-state switching devices. Because of the special design, the straight- through transformer of the function module covers the lower main circuit connection. The cable to the load is simply pushed through and secured with the terminal screw. In the case of internal setpoint selection, the module is controlled over the IN terminal. Terminal 10 has no function.
External setpoint selection With external setpoint selection (potentiometer P far left = 0 %) the module is actuated by applying the analog voltage 0 ... 10 V. 0 ... 10 V corresponds to 0 ... 100 % power. Conversion of the voltage is linear between 0.1 and 9.9 V. Below 0.1 V the swit- ching device remains off; at voltages above 9.9 V the power is always set to 100 %. ■ Function Power control The power controller sets the load current of the solid-state swit- ching device depending on a setpoint value as a percentage. It does not compensate for changes in the mains voltage or load resistance.
The modulation, the On/Off ratio or the phase angle, remains unchanged according to the setpoint value. The auto- nomous power control is performed between 0 and 100 % of the setpoint selection. Inrush current limitation The ramp time (t R ) for a voltage ramp on switching on is set with the left potentiometer for the purpose of inrush current limitation. The set time refers to a power of 100 %. If, for example, a ramp time of 10 s is set and the power setpoint selection is 60 %, then the power of 60 % will be reached after approx. 6 s.
Full-wave control Line, load and thyristor monitoring If the left potentiometer t R is set to 0 s (= far left), then the power controller operates according to the principle of full-wave cont- rol. The power set, be it internal or external, is converted into a pulse-width-modulated digital signal. The power controller con- trols the On and Off time of the solid-state switching device wi- thin a fixed period duration of 1 s so that the selected power is applied to the load. The "ON" LED flashes in the same rhythm as the solid-state switching device switches on and off. The power controller identifies partial load faults, mains failure and thyristor faults.
The faults are indicated by the LEDs on the module and the fault output is actuated. The reference for the load monitoring is the taught value. A maximum of 6 partial loads can be monitored. The response delay in the event of a fault amounts to approx. 100 ms in the case of full-wave control. In the case of genera- lized phase control and setpoint values > 50 % the response de- lay amounts to 500 ms from the end of the ramp time. The detection of partial load faults takes place only in the control range from 20 ... 100 %. 49 Siemens · 2009