ABB PM825-1 3BSE010800R1 Serial Link Module

The command value 6 is a differential input (0 to ± 10 V). If the command value is presented by a separate electronics with a different reference potential, this input must be used. When switching off or on the command value voltage it must be taken care that both signal lines are either separated from or connected to the input. The command values are summated with the corect value and sign before they are connected further [2]. The added ramp generator [3] produces a ramp-like output signal from the jump-like presented input signal. The time constant can be set with the potentiometer "t". The ramp time given refers to a command value jump of 100 % and can be - according to setting through the selection via jumbers - approximately 1 s or 5 s. If a command value smaller than 100 % is switched onto the input of the ramp generator the ramp time is shortened appropriately.

When using an external ramp time

 potentiometer the internal potentiometer for the ramp time must be set at maximum. The maximum ramp time decreases, because the resistance of the external potentiometer is connected in parallel to the internal potentiometer! By switching the relay K5 with 24 VDC (smoothed) or through an external bridge the ramp time is set to its minimum value (approx. 30 ms). The output signal of the ramp generator [3] goes parallel to the summator [5] and the step function generator [4]. The step function generator produces with command value voltages of > ± 1 % a polarity-dependent constant jump signal which is added to the output signal of the ramp generator. This jump function causes the rapid travelling across the overlapping area of the valve.

The output signal of the summator [5] 

is the command current value and is led to the two current output stages [6] and to the test point "w" on the frontplate of the card. A voltage of 6 V at the command value test point corresponds to a command value of 100 %. A positive command value signal at the input of the amplifier controls the output stage for solenoid "B", and a negative signal controls the output stage for solenoid "A". When the command value signal is smaller than ± 1 % (step function still ineffective) a pilot current of 20 mA flows through both solenoids. The actual values of the currents through both solenoids can be measured separately at the sockets IA (solenoid "A") and IB (solenoid "B"). Here a current of 800 mA corresponds to a voltage of 800 mA.

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