6-4.2 Arc Chute Inspection - Eaton MDN-408 Instructions For Installation, Operation And Maintenance

Charge the breaker mechanism springs either using the
charging handle or the motor operator. Close the break-
er by applying rated voltage to the spring release acces-
sory and verify closing by noting the state of the indicat-
ing flag. Charge the breaker mechanism springs either
using the charging handle or the motor operator. If
using the motor operator, disconnect power to it to pre-
vent automatic recharging. Open the breaker by apply-
ing rated voltage to the shunt trip accessory. Close the
breaker using the spring release accessory. Is the
breaker closed? Open the breaker using the shunt trip
accessory. Is the breaker open? Repeat this entire
described test procedure three times.
Trip Unit Overload Functional Test
This test uses the Digitrip 1150 self test function, the
Digitrip Test Kit or the handheld Magnum Functional
Test Kit. Review test kit instructions for the trip unit.
Instruction leaflet 5720B55, section 1.2 or 1.3 applies for
instantaneous test procedures or paragragraph 5.2.1
"1150 Self Testing, Trip Mode" in the trip unit instruction
leaflet 70C1036.
Charge the breaker mechanism springs either using the
charging handle or the motor operator. Press the ON
pushbutton to close the breaker manually and verify
closing by noting the state of the indicating flag. Charge
the breaker mechanism springs either using the charg-
ing handle or the motor operator. If using the motor
operator, disconnect power to it to prevent automatic
recharging. Trip the breaker with a trip unit test. Verify
that the trip indicator pop out button (if so equipped) is
"out" and then reset it. Press the ON pushbutton to
manually close the breaker. Is the breaker closed? Trip
the breaker with a trip unit test. Verify that the trip indi-
cator pop out button (if so equipped) is "out" and then
reset it. Repeat this entire described test procedure
three times. Reset the blinking red cause of trip LED on
the trip unit by pressing the Reset/Battery Test pushbut-
ton.

6-4.2 ARC CHUTE INSPECTION

When a circuit breaker experiences a high level fault or
during regularly scheduled maintenance periods, the cir-
cuit breaker's arc chutes and arc chambers should be
inspected for any kind of damage or dirt. Be especially
alert for signs of significant erosion of the V-shaped
plates inside the arc chute.
Arc chutes fit inside the arc chambers and down over a
the primary contacts. Each arc chute is held in place by
either 1 (MDS) or 4 (MDSX) top inserted screws (Figure
6-1 shows MDS). Begin by removing the arc chute
screws and all three arc chutes. Turn each arc chute
upside down to visually inspect the inside (Figure 6-2).
I.B. 2C12060H08
Since the arc chutes are removed, this is an ideal time
to inspect primary contacts for wear using the circuit
breaker's contact wear indicators. The details associat-
ed with primary contact inspection are presented in the
next paragraph.
For more information visit: www.EatonElectrical.com
Effective: May 2006
Arc Chute
Removed
Figure 6-1 Top Rear View of Circuit Breaker with One
Arc Chute Removed
Figure 6-2 Bottom View of Arc Chute
Instruction Book
Page 62
Baffled
Cover
Arc Chamber
Alternating
"V" Shaped
Plates