–2–
M-0329B Instruction Book
2.1
Installation
The mounting and outline dimensions are shown
in Figure 2, and the external connections in Figure 4.
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NOTE:
TB refers to Terminal Block numbers
shown in Figure 4 External Connections.
The M-0329B can be connected as a two-terminal
device, by paralleling the Power Input (TB1-1 to
TB1-2) and the Voltage (Sensing) Input (TB1-3 to
TB1-4). With this connection, the
BANDCENTER
and the
BANDWIDTH
controls can be set so that
an upper voltage and a lower voltage limit are
established at the desired levels. The M-0329B will
block any further tapchanger raise operations when
the regulated voltage exceeds the upper voltage
limit. Also, if the voltage drops below the lower
limit, the M-0329B will block any further lower
operations. Additionally, if the voltage level
increases above the upper limit (Block Raise) the
M-0329B will lower the voltage, protecting
customers from excessively high voltage levels.
The M-0329B also provides the First Customer
Protection function that previously required a
separate relay. If the LDC raises the local voltage
due to heavy load current, the M-0329B will protect
nearby customers from high voltage, and will act
as an LTC control around the upper voltage limit.
On controls where compensated voltage from the
line drop compensator is available, the M-0329B
can be connected as a four-wire device. The Power
Input should be connected to a 120 V ac source
and the Voltage Input is then connected to the
LDC compensated voltage.
Since sudden changes in the transformer primary
voltage may move the secondary voltage outside
the range of the LTC control and the M-0329B, a 3
minute timer is provided to allow a normal control
to correct the voltage. After 3 minutes of abnormal
voltage, the M-0329B
ALARM
contact will indicate
an abnormal condition. The
BLOCK RAISE/
LOWER
LED will be on, the
ALARM
relay contacts
TB1-14 to TB1-15 will be closed and TB1-15 to
TB1-16 will be open. The
ALARM
contacts will
also indicate an alarm condition if the AC power to
the M-0329B fails.
The
ALARM
contacts should be used to alert
system operators that a problem has occurred and
that the LTC transformer or regulator is not
operating. It must be recognized that the
ALARM
contacts may operate under conditions of heavy
load using the two-wire connections and the line
drop compensator.
The output blocking contacts should be connected
in series with the raise and lower contacts from the
LTC control. In some control circuits, a timing relay
is used. There, the blocking contacts should be in
series with the timing relay contacts. The blocking
relay contacts should not be connected to drop out
the motor starter relay once it is sealed in for a
tapchange, since most tapchangers should not be
stopped until the tapchange is completed. An
exception to this is a spring-driven tapchanger that
may be stopped at any time. Figure 6 shows the
connections for using the M-0329B with most of
the Beckwith Tapchanger and Regulator Controls.
When power is suddenly changed from raise to
lower, motors with centrifugal starters will continue
to run in the wrong direction without reversing. A
defective control timer, for example, could lead to
this type of runaway situation. Here, the M-0329B
will open up the wrong connection if connected as
described above. The circuit of Figure 7 may be
used instead, where timer relay KX permits the
motor to stop regardless of its direction. It is
assumed that the motor will start in the right direction
once it has stopped.