Siemens ET 200SP Manual page 46

Current control
You can use the current control function to proportionally control the power transferred to an
inductive or resistive load. Thermal effects are automatically regulated out.
The setpoint of the current is specified by the user program. The module controls the duty
cycle of the PWM signal according to the setpoint and the reaction depends on the PID
parameters.
The PID controller compares the setpoint and the measured value of the load current to one
another. If the resulting difference is outside a symmetrical dead band, a reaction of the
controller is calculated by taking into account the enabled components of the PID controller
(proportional, integral and/or differential).
The calculated manipulated variable value is subject to defined high and low limits. If the
manipulated variable value reaches a limit, the user program reads this in the feedback
interface (Page 58) via the QLMN_HLM and QLMN_LLM bits.
You set the parameters for the current control in the hardware configuration. The value of
OUTPUT_VALUE in the control interface (Page 55) is interpreted as the current setpoint
relative to the reference value of the current.
The figure below shows the principle of operation of the PID current control.
Technology Module TM Pulse 2x24V (6ES7138‑6DB00‑0BB1)
Manual, 05/2019, A5E35061186-AB
Configuring/address space
4.2 Pulse width modulation PWM mode
45