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The user must determine the specific setting s which will provide the required protect ion for his
�achine, and select a relay model having the operating ranges needed to obtain these settin gs.
With settings as illustrate d in Figure 9 and external connections shown in Figure 10, the operation of
�""
IFC66K relay will be as follows:
For motor overloads the time overcurrent unit (51) will time out, picking up an external auxiliary
1.
51X, which sounds an alarm.
* 2.
For the locked rotor condition the high-dr op ou t
TOC unit (51) will pick up with a time delay consis tent with the motor thermal limit.
units have operated the breaker will be tripped.
* 3.
For a fault the normal dropout instantaneous unit (50/A) � ill pick up instantaneou sly and trip the
breaker.
When used as back-up protection, the time overcurrent unit IFC66 should be set to coordinate with down
stream protective devices.
The following factors must be considered in determining a setting:
•
Operating time of the downstream relay and breaker
•
Overtravel in the induction disk unit
•
A safety factor to allow for variations in system parameters from the values used to determine the
relay setting.
Relay overtravel is often considered to be less than 0. 1 second; exact values can be read from Figure 11.
Typical safety factors range from 0.1 to 0.2 seconds.
The IFC induction disk relays consist of a molded case, cover, support structure assembly, and a connec
tion plug to make up the electrical connection.
the induction unit mounted to the molded support structure.
cr�, mounted on a laminated U-Magnet.
t
larm or trip circuit when it touches a stationary contact.
spr1ng to give the proper contact closing current.
mounted in a molded housing on the support structure.
The drawout connection/test system for the Cl case, shown in Figure 19, has provisions for 14 connection
points, and a visible CT shorting bar located up front.
shorter contact fingers in the output contact circuits first.
other circuits are disconnected.
ing bar (located at the lower front of the case) to short-circuit external current transformer secondary
connections.
The window provides visual confirmation of CT shorting.
current circuit contact fingers on the case and finally those on the relay support structure to completely
de-energize the drawout element.
There is a Hi-Seismic target and seal-in unit mounted on the front to the left of the shaft of the time
overcurrent unit, see Figure 1.
contacts of the time overcurrent unit such that when the induction unit contacts close, the seal-in unit picks
up and seals in.
When the seal-in unit picks up, it raises a target into view which latches up and remains
exposed until released by pressing a reset button located on the upper side of the cover.
The IFC "B" and "K" model relays in addition to the above contain a Hi-Seismic instantaneous unit, see
Figure 1.
The instantaneous unit is a small hinged type unit which is mounted on the front to the right of
the shaft of the time overcurrent unit. Its contacts are normally connected in parallel with the contacts of
the time overcurrent unit and its coil is connected in series with the time overcurrent unit.
instantaneous unit picks up it raises a target which latches up and remains exposed until it is released. The
same reset button that releases the target seal-in unit also releases the target of the instantaneous unit.
The IFC "K" model rela ys in addition to the above contain a Hi-Seismic dropout
high dropout instantaneous unit is a small hinged type mounted in the rear of the relay, see Figure 2.
Unlike the Hi-Seismic instantaneous unit, this unit does not include a target and therefore does not have to
be rP-set after it operates.
,�
magnetic shield, depicted in Figure 1, is mounted to the support structure, to eliminate the proximity
affect of external magnetic materials.
- ------ - --------·---------�-- --�--- - --- -
GEK-45376
A minimum coordinating time margin of 0.2 to 0.4 seconds will normally be required.
CONSTRUCTION
See Cover Figure and Figures 1, 2 and 19.
The disk and shaft assembly carries a moving contact which completes
Next, current circuit fingers on the case connection block engage the short
The seal-in unit has its coil in series and its contacts in pa rallel with the
---·--- ------ ---- �----- -------�-·----�
u nit (50/B) will pick up instantaneously and the
The disk is activated by a current operating
The disk assembly is restrained by a spiral
The disk's rotation is retarded by a permanent magnet
As the connection plug is withdrawn, it clears the
Thus, the trip circuit is opened before any
The connection plug then clears the
4
When both
Figure 2 shows
When the
instantaneous unit.
The
t
•
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