Eaton EVER-Tap Installation, Operation And Maintenance Instructions page 21

Voltage circuits
Eaton voltage regulators have provisions for operation at
system voltages other than the nominal rating, as listed
in Table 9 (page 36) and Table 10 (page 37). This is
accomplished by providing taps on the control winding or
PT. The taps are brought to a terminal board located on top
of the tap-changer assembly, under the insulating fluid, and
are marked E1, E2, or E3. (See Figure 18.) The connections
are made with push-on terminals and are easily accessed
through the hand hole.
Figure 18 . PT tap terminals on a QD3 tap-changer
If an additional potential transformer is required for a
Reverse Power Flow application or indication of the
unregulated voltage supply, the "P" taps will be located
either on a separate voltage transformer or on the
tap-changer terminal board.
The PT cannot always provide adjustment of the voltage fine
enough for control or motor use. A tapped autotransformer
is used for fine voltage adjustment. This transformer, the
Ratio Correction Transformer (RCT), has input taps at 104,
110, 115, 120, 127 , and 133 V. The output tap to the control
and motor is set as 120 V. The RCT is located on the control
back panel (see Figure 10 and Figure 11).
To operate a regulator on a system voltage other than its
nominal rating, the appropriate selection must be made for
the PT and RCT taps and the control must be programmed
properly at Function Code (FC) 43 (System Line Voltage),
FC44 (Overall PT Ratio) and FC44 (Internal PT Ratio). The
nameplate provides settings for common system voltages
(see Figure 8 and Figure 9).
The internal voltage supply is brought from the tap-changer
terminal board through the junction box and the control
cable, into the control box, terminating at the knife switch
labeled V1 (and V2, V6, and V8 if provided). Opening this
knife switch provides a visible means of removing all power
to the control and motor circuits. From the knife switch, the
voltage is ratio corrected by RCT as previously described.
Most voltage regulators are installed in circuits with well-
defined power flow from source to load. However, some
circuits have interconnections or loops in which the direction
of power flow through the regulator may change. For
optimum utility system performance, a regulator installed on
E Taps
InstallatIon, operatIon, and MaIntenance InstructIons MN225008EN June 2020
VR-32 and EVER-Tap™ Voltage Regulator
such a circuit should have the capability of detecting reverse
power flow and of sensing and controlling the voltage,
regardless of the power flow direction. The CL -7 control has
full reverse power capabilities.
Refer to Service Information MN225003EN, CL -7 Voltage
Regulator Control Installation, Operation, and Maintenance
Instructions, for more information on the CL-7 control,
reverse power operation, and source-side voltage
calculation.
On the front panel, the three potentials (VS, sensing
voltage; V7, differential voltage; VM, motor voltage) are all
brought directly to the power switch. Without an optional
source-side supply, the V7 terminal is connected to the VS
terminal on the control back panel and the control software
then recognizes that a source-side voltage signal is not
present.
The power switch has three positions: INTERNAL, OFF ,
and EXTERNAL. The internal position powers the control
and motor from the regulator sensing winding, and the
external position permits an external supply for the same
purpose. When the power switch is in the external position,
the internal supply is disconnected to prevent accidentally
back-feeding the high-voltage winding and bushings. The
external-source terminals are prominently located adjacent
to the voltmeter test terminals.
The voltmeter terminals allow the monitoring of the voltage
that is applied to the control. This is the voltage output
from the RCT and the voltage displayed at FC47 (Voltage
Calibration). During forward power flow, the voltage at these
terminals is the output voltage. During reverse power flow,
the voltage at these terminals is the source-side voltage.
From the 6 A fuse, the motor potential provides power
to the CONTROL FUNCTION switch, the drag-hand reset
solenoid, the neutral light, and the holding switch (alternate
motor source) circuits.
Electrocution Hazard . Applying voltage to the voltmeter
terminals on some voltage regulator controls can back-
feed the voltage regulator potential transformer and
create high voltage on the bushings . When applying
external power to the voltage regulator control, make
sure to open the V1, (and V2, V6, and V8 if present)
switches on the back panel, apply power to the external
source terminals only and move the POWER switch to
EXTERNAL .
WARNING
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