QD3 Quik-Drive Voltage Regulator Tap-Changer Manual
4
Motor Capacitors
The QD3 tap-changer uses two different motor capaci-
tors depending on whether the tap-changer is being
used with 50 Hz or 60 Hz power. The motor capacitor is
not part of the tap-changer assembly. The capacitor for
regulators supplied with a QD3 tap-changer will be found
in the voltage regulator control box assembly.
Capacitor Size
Power Size Rating
50 Hertz 15 ufd 440 Vac 100 °C
60 Hertz 12 ufd 440 Vac 100 °C
It is important to use the correct size capacitor with the
QD3 tap-changer hanger. For example: If a 12 ufd is used
on a tap-changer that is being applied to a 50 Hz sys-
tem, the tap action of the tap change can be affected by
the number of steps taken and the directional operation
of the tap-changer. The same can occur if a 15 ufd is
used for a 12 ufd on a 60 Hz system. Other problems can
occur if smaller or larger capacitors are used in place of
the specified capacitor size. It is always recommended to
use the motor capacitor supplied by the manufacture of
the tap-changer and voltage regulators.
QD3 Motor Resistor
Resistor Size:
40 Ohm
100 Watt
The motor resistor on the QD3 tap-changer is used for
proper phasing of the motor. An open resistor, resistor
connection, or different size resistor will affect operation
of the motor. Either of these conditions can cause the
motor to take more tap steps then required as well as
causing the motor to run or start to run in the opposite
direction.
Holding Switch
The QD3 tap-changer uses a micro-switch assembly for
the holding switch instead of a three-blade contact hold-
ing switch assembly that was used on the spring drive
tap-changer assembly. The micro-switch assembly elimi-
nates the need and requirements for making adjustments
in the alignment and gape settings when working on or
around the holding switch assembly.
All Cooper Power System tap-changers are equipped
with a holding switch to assure that a tap-changer in pro-
cess is completed. This switch also provides a repetitive
and accurate opening action causing the motor to stop
the drive components with correct alignment. A signal
from the holding switch activates the operations counter
and prevents time delay reset during a tap change. The
holding switch is operated by a pinion cam causing the
holding switch lever to close in on either the raise or lower
micro-switches. If a holding switch needs to be worked
on due to problems with one of the two micro-switch-
es, the micro-switch should not be replaced with a new
one. The complete assembly needs to be replaced with a
micro-switch assembly from the factory. Replacement of
the micro-switch can cause problems with the assembly
and tap-changer. Special fixtures are used for the assem-
bly to prevent alignment gap setting requirements.
Figure 3.
Motor resistor.
CAUTION:
Operating the QD3 Tap-Changer in air for an
excessive amount of time, or if operating continues
without pulsing, will cause the resistor to become
hot to the touch. Overheating can be a harasser
causing injury if touched and can affect the
operation of the tap-changer motor.
Actuator
Lever
Micro Switch
Micro Switch
Figure 4.
Holding switch assembly.
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