Current Regulation Of A Valve - Siemens SIMATIC ET 200S Operating Instructions Manual

5.7.6

Current regulation of a valve

Preliminary remark
In order to successfully design a control loop for current regulation of a valve, corresponding
knowledge of control technology and the concrete control task is required.
Description
A proportional valve is used to control the pressure in a vessel. In order to compensate for
thermal effects in the valve, it is addressed with a controlled current. Together with the
higher-level control loop (pressure control), a cascade control system results in which the
current regulation of the valve forms the inner component. The structure of the higher-level
pressure control is not addressed in this example.
The valve is controlled directly through the 24 V control signal of the 2PULSE. Pulse width
modulation is selected as the operating mode. The execution of the current measurement
required for the control is integrated in the 2PULSE.
For the higher-level pressure control, an analog input module detects the data from a
pressure sensor mounted correspondingly. The pressure measured values determined are
input to the pressure regulator that runs on the CPU.
In order to achieve particularly high-performance control, 2PULSE can also be operated in
isochronous mode (see section "Isochronous mode (Page 267)").
Figure 5-33
Technological Functions
Operating Instructions, 06/2010, A5E00124867-07
Application example with current-controlled valve
2PULSE
5.7 Application Examples
341