6. Function blocks
6.1 Manufacturer function blocks
6.1.4.4 TC - Three step controller
General
easyE4 base devices provide 32 three-step controller function
blocks, TC01 through TC32.
TC three-step controllers feature three states for the manipulated
variable. These states are implemented with two function block out-
puts Q1, Q2, of which either none or only one can be closed. I1 is
the setpoint and I2 is the actual value. X = I1 - I2 yields control devi-
ation X, which is applied on the actual controller. The controller will
then determine the manipulated variable for function block outputs
Q1, Q2.
Fig. 202: Three-step controller schematic diagram
I1: Setpoint
I2: Actual value
Operating principle
The following timing diagram shows how the three-step controller behaves.
Fig. 203: Timing diagram for three-step controller
XH/ -XH: Distance X from switching point
H1: Hysteresis 1 for XH
H2: Hysteresis 2 for -XH
Y(t): Operating points for Q1/ Q2
easyE402/24 MN050009ENEaton.com
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