Melitta LOOK - Connections for MVTU 11, MVTU 12 and MVTU; General Procedure and Precautions; Inspection - Removal of Module from Case

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6.2 General procedure and precautions
Care must be taken when making test connections to printed circuit boards to avoid
short circuiting or damaging the copper tracks. Before connecting or disconnecting
any test equipment the relay must be isolated from the supply.
Relevant schematic diagrams
MVTU 11 – Undervoltage – F10 MVTU 11 501 Figure 5
MVTU 12 – Overvoltage – F10 MVTU 12 501 Figure 6
MVTU 13 – Neutral displacement – F10 MVTU 13 501 Figure 7
MVTU 18 – Neutral displacement – F10 MVTU 18 501 Figure 8
6.3 Inspection – removal of module from case
Unscrew the two front cover screws and remove the clear plastic front cover.
Ensure that the dc supply is isolated and then withdraw the module assembly by the
two black handles. A quick inspection of the relay may result in the detection of
obvious faults. i.e. loose components or connections. Otherwise proceed to the next
section.
6.4 Connections for MVTU 11, MVTU 12 and MVTU 13
There are two classes of relay connection. Firstly, the external connections to the
relay; these are the connections between the relay terminals and the rest of the
system.
Secondly, the printed circuit board connections; these are the connections between
the relay terminal block and the printed circuit board soldered connections.
Terminal connections: Terminals 13 and 14 are connected to the positive and
negative dcsupply. Terminals 1 to 6 are the tripping
outputs of the relay. Terminals 27 and 28 are the ac input.
PCB connections: There are six loop and bead connectors mounted on the
pcb. They are connected as follows:
Connection 1 to terminal 13 – positive dc supply
Connection 2 to terminal 14 – negative dc supply and to
pcb ZG7001
Connection 3 to pcb ZG7001
Connection 4 pcb ZG7001
Connection 5 to terminal 27 – ac input
Connection 6 to terminal 28 – ac input
Connections for MVTU 18
Terminal connections: Terminals 13 and 14 are connected to the positive and
negative dcsupply. Terminals 1 to 6 are the tripping
outputs from timer t
1
. Terminals 7 to 12 are the tripping
outputs from timer t
2
. Terminals 27 and 28 are the ac
input.
PCB connections: The MVTU 18 has 2 printed circuit boards. ZJ0065
contains the measuring circuit and the circuit for timer t
1
.
ZJ0160 contains the circuit for timer t
2
and the output
relays for t
1
and t
2
.