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The IBCG relays consist of two units, a time overcurrent unit (top) of the
induction disk type,
induction cup type.
both and, by means of its closing contacts, directionally controls the operation of the
time overcurrent unit.
The IBCG relays have a target seal-in unit
shown by Table 1, have a hinged armature type instantaneous overcurrent unit.
The IBCG relays are mounted in the single-ended Ml drawout case.
DIRECTIONAL UNIT
.
The directional unit is of the induction-cylinder construction with a laminated
stationary central core.
the annular air gap between the poles and the core.
operating, current polarizing and potential polarizing coils.
The principle by which torque is developed is the same as that of an induction
disk relay with a wattmetric element, although, in arrangement of parts, the unit is
more like a split-phase induction motor.
higher torque and lower rotor inertia than the induction-disk construction resulting in
a faster and more sensitive unit.
CONTACTS
The directional unit contacts which control the time overcurrent unit are shown in
*
They are of the low gradient type, specially constructed to minimize the
effects of vibration.
gradient material which,
hence, they resist contact separation.
The contact dial (A) supports the stationary contact brush (8) on which is mounted
a conical contact tip (C).
brush (E) on which is mounted a button contact tip (F). The end of the moving contact
brush bears against the inner face of the moving contact brush retainer (G).
Similarly, the end of the stationary contact brush bears against the inner face of the
stationary contact brush retainer (H).
dial, functions to stop the motion of the contact arm by striking the moving contact
brush retainer after the moving and stationary contact members have made contact.
stationary contact support (K) and the contact dial are assembled together by means of
a mounting screw (L) and two locknuts (M).
TIME OVERCURRENT UNIT
The inverse time and very inverse time overcurrent units consist of a tapped
current operating coil wound on a U-magnet iron structure. The tapped operating coil
is connected to taps on the tap block.
are connected in series with'a directional unit contact. When power flow is in such a
direction as to close the directional unit contacts, the shading coils act to produce a
split-phase field which, in turn, develops torque on the operating disk.
*Indicates Revision
CONSTRUCTION
and an instantaneous power directional unit (bottom) of the
The directional unit is either potential or current polarized or
The cuplike aluminum induction rotor is free to operate in
Both the stationary and moving contact brushes are made of low
when subjected to vibration, tend to follow one another,
The moving contact arm (D) supports the moving contact
The U-magnet contains wound shading coils which
11
models with the YlA suffix, as
The poles are fitted with current-
The induction-cylinder construction provides
The stop screw (J), mounted on the contact
The
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