Westinghouse KC-4, Installation, Operation & Maintenance Instructions Manual

Page: 154 / 178

It can be energized continuously at 1 1 0% of
rated input voltag1�.
Capacitive Effec1t
The capacitive surge immunity is as follows
(considering the 52a contact input present):
Relay Rating BF
Timer Setting Capacitance
48
Vdc 1 8
ms or higher 1 8
M FD
1 25
Vdc 1 8 ms or higher
6 MFD
1 25
Vdc 35
ms or higher 1 3
M FD
250
Vdc
1 8
ms or higher 2.5
MFD
250
Vdc 35
ms or higher 1 3
MFD
Any value of capacitance effectively in series
with the input greater than that shown above
might result in an undesired trip operation.
Ordinarily capacitance should not be con­
nected from the lead connecting the 52a contact to
the relay and ground. A value of 0.5 M F D could
cause the 52a input to stay on for 1 .5 ms (48V
relay), 4 .5 ms ( 1 25 V relay) and 20 ms (250V relay)
after the 52a contact opened.
X
RELAY
Coil resistance is 1 500 ohms ±5%
a
n
d rated
for
24Vdc operation . The seal-in contact will
pickup providing the B F I (62X, 62Y) initiate con­
tacts are closed for a minimum of 8 ms. A second
0
contact is wired to relay terminal 1 1 and 1 2 to
provide a retrip feature.
AR R E LAY
The coil resistance is 630 ohms ±5% and will
operate in series with the appropriate resistor
from 80% to
I I
0% of rated voltage.
The operate spe{�d is 3 to 5 ms at rated voltage.
The dropout time is 30 to 45 ms (diode around the
coil). There are 4 normally open contacts
available.
I NDICATI N G C ONTACTOR SWITC H ( I C S)
The coil resistance is approximately 6.5 ohms
4
on the 0.2 amp tap and 0. 1 5 ohms on the 2.0 amp
tap.
TRIP C I RCUIT
The main contacts will safely close 30 amperes
at 250 V de and the seal-in contacts of the I CS will
safely carry this current long enough to trip a cir­
cuit breaker.
SETT I N G S
OVERC U R RENT DETECTOR
The pickup of the overcurrent unit is obtained
by means of a tap screw and tap block in conj unc­
tion with the tap multiplier knob setting located at
the front of the overcurrent unit module. This per­
mits a contin uous adjustment over the range o f 0.5
to 1 3 .5 amperes. Each tap setting permits ad­
justing the pickup over a 3 to 1 range.
There are 2 or 3 phase inputs depending on the
relay style. Each one has its own tap block . N or­
mally all the phase settings should be in the same
tap. The operate point for each phase should be
within 5% of each other. There are trimpots for
each input located on the overcurrent module
which are factory adjusted but which may be read­
justed if the 5% accuracy must be improved at any
one pickup point.
The
ground u
n
i
t p
i
c
kup is obtained similar to
the phase above and is independent of the phase
pickup. This permits the ground setting to be lower
than the phase setting.
The phase units must be set below th e
minimum expected fault current and the ground
unit set below the minimum expected residua l
(3 10) current. Settings should b e made t o assure
a
multiple of pickup of at least 2 under minimum
fault conditions.
C ONTROL TIMER
The control timer can be set by use of a screw ..
driver to adjust the trimpot which is accessibk
through the h ole in the front plate of the timer
module. Clockwise rotation will increase the on
time. An oscilloscope or electronic timing devic(�
can be connected between the bottom red test jack
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