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VR-32 and EVER-Tap™ Voltage Regulator
Quik-Drive tap-changer mechanism
A tap change is initiated by the Control. After some rotation
of the drive gear connected to the motor, a holding switch
energizes the motor through a separate circuit until the
indexing motion is completed. The indexing occurs very
quickly. The total elapsed time to complete the action is
approximately 250 milliseconds from the time the indexing
signal is started by the control. Each full turn of the Geneva
drive gear rotates the main Geneva/contact drive assembly
one tap position, which is 20 degrees.
Reversing switch
The reversing switch function changes the polarity of the
tapped winding. When a Quik-Drive tap-changer is in the
neutral position, the reversing switch is open.
The reversing switch motion on the Quik-Drive tap-changer
occurs as the main movable contacts enter or leave the
neutral position. The Main Contact Assembly engages the
Reversing Switch either directly or through a linkage when
the main switch is in the neutral position. The first tap step
in either direction rotates the Reversing Switch Assembly to
engage the appropriate contacts.
Additionally, the Main Contact Assembly, or its drive, and
the Reversing Switch Arm provide a mechanical stop located
320° on either side of the neutral position so that the
tap-changers cannot be moved past 16 Lower or 16 Raise.
Quik-Drive motors drive systems
Either an alternating current (AC) synchronous motor or
an induction motor is used on Quik-Drive tap-changers.
The motors use a holding switch circuit that is activated
by a pinion cam closing holding switches as the motor
begins to rotate. The holding switch is engaged throughout
the duration that the movable contacts are in motion to
ensure that the tap change cycle is complete. Because of
differences in rotational speed and braking characteristics,
the AC synchronous motor uses a cam of different timing
duration than the induction motor to activate the holding
switch. The cam on the AC synchronous motor is engaged
for 270° of rotation while the induction motor cam is
engaged for 105° of rotation.
The AC synchronous motor utilizes a phase-shifting network,
consisting of a capacitor and a resistor, to operate properly
when powered by a single-phase source. This motor has
a permanent magnet rotor that arrests the inertia of the
system once power to the motor is removed; therefore, no
braking mechanism is required. The AC synchronous motor
uses a 12 µF capacitor for 60 Hz applications and a 15 µF
capacitor for 50 Hz applications.
The induction motors use a phase-shifting capacitor and
require a friction-type brake to stop the motor between tap
changes. Brakes use various means to interrupt the braking
action while the movable contacts are in motion so that full
motor torque is dedicated to completing the tap change.
The induction motors use a 50 µF capacitor for 50 and 60
Hz operation.
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InstallatIon, operatIon, and MaIntenance InstructIons MN225008EN June 2020
Contacts
Several connection conditions are satisfied by the variety
of contact structures. They are divided into arcing and
non-arcing.
The non-arcing contacts consist of front and rear slip rings,
which serve as the connection point for opposite ends of
the reactor windings and one end of the two main movable
contacts. All contact surfaces are Electrical Tough Pitch
(ETP) copper and all joints are riveted, bolted, or brazed to
maintain a high-conductivity current path. Contact pressure
between moving points is maintained by opposing steel
compression springs.
There are several types of arcing contacts on a regulator
tap-changer. They can be divided into two categories: main
and reversing.
The main stationary contacts are connected to the series-
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winding taps. The main movable contacts connect the slip
rings to the main stationary contacts.
The reversing stationary contacts are connected to
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opposite ends of the series winding. The reversing
movable contacts connect the neutral stationary contacts
to the reversing stationary contacts.
All stationary contact bodies are made of ETP copper.
Copper-tungsten inserts are brazed to the edges of the
stationary contacts since those contacts are subject to
damage from impact or arcing duty. The main movable
contacts are constructed of a copper-tungsten. The movable
contacts are split to make connection on both sides of the
stationary contacts. This split resists separation in the event
of high-current surges.
The tap-changer stationary contact body is copper. The
reversing movable contacts are the same construction as
the main movable contact.
Contact erosion is a function of many variables such as
system parameters, regulated and unregulated voltages,
line currents, power factor, voltage and current harmonics,
and reactor and main core and coil designs.
Stationary contacts should be replaced before the arcing
inserts erode to the point where there may be burning on
the copper. Movable contacts should be replaced when
approximately 1/8 inch of smooth surface remains.
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