set to such a position when reliable cutting out of the position switch takes place and which is still acceptable for the piping
fitting. Herein, the position and moment switches are connected in series. This can only be realized in the case when
a tightly closed piping fitting is not required.
b) Position switches
Position end switches PO, PZ are used for cutting out the electric actuator when it reaches the position of the output
shaft of the electric actuator for which it is set.
The signalling switches SO, SZ are used for signalling the position of the output shaft of the electric actuator.
The position switches are adjusted in such a way that the output shaft is first set to the position where the switch being
adjusted should cut out. Then, the micro-switch cam is released by a particular releasing screw. Releasing is carried out
by turning the releasing screw counterclockwise. The releasing screw should only be turned to the extent sufficient for
releasing the cam. Further turning of the releasing screw would result in retightening the cam.
The signalling switch should be set so that it switches over earlier than the particular position end or moment switch. When
adjusting the position and signalling switches of the electric actuator type no. 52 321, care should be taken that the geared
segment of drive of the position and signalling unit in the limit position “Closed” or “Opened” does not strike against the electric
motor jacket. For the electric actuator type no. 52 320 the cams are secures by friction and by a central grooved nut with
a safety nut which should be released during adjusting. After adjusting they should be properly retightened.
c) Position transmitters
Resistance transmitter
For setting the resistance transmitter of position it is sufficient to reset the output shaft of the electric actuator to either
of the end positions “Opened” or “Closed”. In this way the transmitter of position is automatically set. This is usually done
in setting the stop screws or the position end switches.
Setting of current position transmitter CPT 1A.
Before starting setting the current transmitter it is necessary to set the end-limit positions
(torque or position switches)
of the actuator and connect them into the tripping circuit of the electric motor. In case of an external source of feeding
voltage, verification must be carried out that it does not exceed the maximum value 30 V DC
(limit value when CPT 1A is
still not damaged).
Recommended value is 18 – 28 V DC.
Positive pole of the source is connected to the positive pole of the transmitter CPT 1A; a milli-ammeter of precision at
least 0.5 % connected into the circuit. The current loop must be earthed in one point. The figure does not show the earthing
that can be made at any point of the circuit.
1.
Shift the output shaft into the position Closed. During closing, the current signal value should decrease. If it increases
release the transmitter body and, by turning of about 180°, shift to the descending part of the outputcharacteristics. Set
4 mA by fine turning. Tighten the shim plates to secure the transmitter against spontaneousturning.
2.
Shift the output shaft to the position Open and set 20 mA using a potentiometer on the transmitter body.
The potentiometer has a range of 12 revolutions and it has no stops so that it cannot be damaged by furtherturning.
3.
Once again verify the current value in the position Closed. If it has changed too much repeat the points 1. and 2. If the
required corrections are large this procedure should be repeated several times. After the setting, securethe transmitter
against turning and drip the screws with varnish.
4.
Use a voltmeter to check the voltage on the CPT1 terminals. In order to keep linearity of the output signal the voltage
must not drop below 9 V, not even with off-take 20 mA. If this condition is not met it is necessary to increase the feeding
voltage
(within the range of recommend values)
or to decrease total resistance of the current loop R.
11
CPT 1A
U
U
R
mA
V
R
red
51
51
52
52
red
white
white
CPT 1A
Summary of Contents for Modact MOKP 100 Ex Series
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