Effective 8/2006
Page 20
I.L. 66A7534H04
secondary injection current. This is because of the trip
unit’s “chopper” power supply. The peak hold feature will
hold the trip current level when an auxilary switch from the
circuit breaker is wired back to the tester’s terminals
(white posts) labeled
Contacts
.
3. Also when performing low current secondary injection
tests (less than 2 Amperes) it is desirable to insert an
additional 25 ohm impedance (resistor or inductor) rated at
25 or 50 watts in series with the
5A
terminal post. This will
provide proper impedance for the “chopper” and is useful in
stablizing the current
(See Figure 5.5).
5.4.2.2 Primary Injection Testing
Preliminary hookup:
Figure 5.2 AVO MultiAmp
®
MS-2 Test Source
a. Connect an Aux Switch or unused unused circuit
breaker pole to the
Contacts
input terrminals of the MS-2
current source to hold current ramp value level and to stop
the timer.
contacts and into the Digitrip trip unit. This is a complete
system checkout and is strongly recommended after initial
setup and before enerizating of the gear. Although the MS-
2 source is limited to 600 amperes (momentary), it can
verify that the trip unit powers up properly and perform a
ground fault trip of the circuit breaker. This testing at the
primary injection level is able to verify that the breaker’s
response to each primary phase current is correct. The
secondary injection current source is able to deliver up to
5x (1 ampere is 1 per unit) into the breaker’s secondary
contacts. This can produce a 300% overload test and a
400% Short Time or Instantaneous test.
The following extra components are desirable additions for
the testing.
1. For the primary injection testing, three separate flexable
(welding type) cables (#2 AWG or larger) and each about 3’
(.914m) long, are required to be fabricated. Connectors,
with tabs, need to be attached on each end to connect to
the tester’s terminal studs. The flat tab extension will also
provide a surface to attached to the gear’s bus conductors
using C-clamps. A typical connector style would be an
ILSCO style SLS125.
2. For secondary injection tests, a separate True RMS
ammeter with a “peak hold” feature is required
(See Figure
5.5).
The built in meter of the MS-2 tester is not True RMS
and does not provide an accurate measurement of the
b. Set Digitrip
Ground Setting
to “0.4” and remove (if any)
jumpers connected on secondary points B-6, B-7
(See
Figure 1.6).
c. Connect one end of the primary current cables to the
240A
and
Common
posts of the MS-2 test source.
Connect the other ends to the line and load side of the
breaker’s left pole(Phase “A”). This will provide a primary
current through CH Type-V current sensor for the test.
d. Set MS-2 built-in meter to
750A
scale.
IMPORTANT:
Do the following test even if ground fault is
to be set to
OFF
or Zero Sequence Sensing is chosen for
the final application.
