22
PCB ZJ0065: Connection 1 to terminal 13 positive dc supply
Connection 2 to terminal 14 negative dc supply
Connections 3, 4, 9 and 10 to pcb. ZJ0160
Connection 5 to terminal 27 – ac input
Connection 6 to terminal 28 – ac input
Connection 7 to pcb screen
PCB ZJ0160: Connections 1, 2, 3 and 4 to ZJ0065
Connections 5 to 10: to t
1
output contacts
Connections 11 to 16: to t
2
output contacts
6.5 Checking voltage supplies to module
The dc voltage ratings available are 30/34V, 48/54V, 110/125V and 220/250V.
Where voltage sources which are higher than 30V are used, external dropper
resistors are connected in series with the positive supply rail.
Note that MVTU 18 relays do not require external dropper resistors.
Check that the dc supply voltage is present and that the polarity is correct between
terminals 13 and 14 on the relay case terminal block when the module is removed
from the case. Note that when the module is in the case and the supply is connected,
the voltage across the terminals may be less due to the voltage drop across the
external dropper resister Rext 1 (if fitted).
Check that the ac is present between terminals 27 and 28. Check for the 220/250V
and the 380/440V ac versions of the MVTU 11 and MVTU 12, that the series
resistors are fitted in series with the ac supply terminals.
6.6 Printed circuit board tests
If all the connections are intact and the supplies are of the correct voltage and
polarity, it is likely that the fault will lie somewhere on the pcb. Proceed to the next
two sections to try to confirm this.
6.6.1 Monitoring of the voltage across relay coil
Set the thumbwheel switches to 0.1 seconds. Connect an electronic voltmeter across
pcb ZJ0062 connection 3 and 4 to monitor the output signal. Adjust the ac input to
an amplitude lower and then higher than the relay setting voltage. The output voltage
should change from zero to approximately 24V for the overvoltage (MVTU 12) and
the neutral displacement (MVTU 13) version, and from approximately 24V to zero for
the undervoltage (MVTU 11) version.
6.6.2 Measurement of the dc operating currents of the modules
By monitoring the dc operating current of a module, a good indication is provided
that the module is connected correctly and that the dc power supply section is
operating correctly if the current measured lies within about ±10% of the specified
value. Allowances must be made for supply voltages deviating from the lower rated
voltage as this has a significant effect on the dc burden.
These dc burden tests should be carried out in the operated and non-operated state –
that is with the ac input both above and below the voltage setting level.
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