Effective 8/2006
Page 22
I.L. 66A7534H04
NOTE:
As the MS-2 tester has limited current source
capabilities, testing of the Digitrip 520V and 520MCV could
be assisted by the handheld tester shown on page 16. The
handheld unit, when its connector is plugged into the test
kit input pins of the Digitrip, provides external power to the
trip unit to stabilize the “chopper” power supply. Use the
Power Up
switch position of the handheld and make sure
there is a feedback
Aux Switch
present. This is required to
shut off the MS-2 current source when tripping occurs.
This will also enable higher per unit testing levels.
Equation for trip time @ 300%
“Max. Long Time” trip(sec) =
Long DelayTime
setting X 4
“Min. Long Time” trip(sec) =
Long Delay Time setting X 2.8
The breaker should trip within the above range and “Long
Time” trip LED should flash. Check battery if this cause of
trip LED does not flash.
TEST 4. The “Short Delay” or “Instantaneous” trip
elements (set @ 4x) can also be checked by ramping
current. Close circuit breaker. Place the separate meter in
the “Hold” mode. Ramp current until trip the circuit breaker
trips (expected range of 3.6 to 4.4 A). Appropriate trip LED
should flash.
Test Procedure:
TEST 1. Turn power switch
ON
and ramp up current slowly
looking for the Digitrip’s
Unit Status
LED to flash
consistently at one second intervals. This power up should
occur at 25 to 35% (about 0.3A for this single phase input).
TEST 2. Keep increasing current and note where the
flashing
Unit Status
LED is about four times faster. This
point is the “Long Delay Pickup Point” and is nominally
1.1x
Long Delay
Setting
.
NOTE:
The AVO MS-2 Test Source is not a perfect source,
particularly when it encounters the “chopper” power supply
of the Digitrip so the exact point may be difficult to
determine.
TEST 3. Set the current to 300% which is 3A (+/- 0.1).
Remove or short out the series resistor for the trip tests.
NOTE:
Three Amperes is truly 300% only when the
Long
Delay Setting
is set to 1x. Other 300% test current levels
will need to be calculated if the
Long Delay Setting
is set
other than 1x. Set
Ground Setting
to
OFF,
Instantaneous
to 4x and
Short Delay
Setting
to 8x.
Run 300% overload to trip the circuit breaker on
“Long
Time.”
Figure 5.5 Secondary Injection Test Setup
5A
Current Source
(AVO Type MS-2
or equivalent)
Com
RMS Ammeter
with Peak Hold
Stabilizing
Resistor
Contacts
(Binding Posts)
Circuit Breaker
AUX Switch
25 Ohm - 25W
To Secondary Terminals
of Phase A, B or C
A = A-4 & A-19
B = A-5 & A-20
C = A-6 & A-21
Circuit Breaker
Ammeter
