26
Instruction Book
IB182023EN March 2016 www.eaton.com
AMH-4.76-VR
Replacement Circuit Breaker
6.7 PRIMARY CIRCUIT RESISTANCE CHECK
The main contacts of the VR-Series circuit breaker are inside
the vacuum chamber where they remain clean and require no
maintenance at any time. Unlike most typical circuit breaker designs,
the VR-Series design uses a highly reliable and unique flexible clamp
design that eliminates the need for lubrication and inspection for
wear.
The DC electrical resistance of the primary circuit may be calculated
by measuring the voltage drop across the circuit. This test should
be performed with a low voltage, direct current (DC) power supply
capable of delivering no less 100A DC.
•
To check the primary circuit resistance:
•
Remove the circuit breaker from the switchgear
•
Close the breaker
•
Pass at least 100A DC from terminal to terminal of each pole
unit in the closed position
•
Measure the voltage drop across the terminals.
The resistance can be calculated from Ohm’s Law and is expressed
in micro-ohms. Repeat for the remaining two poles.
The resistance should not exceed the factory test levels more than
200%. Factory test levels are recorded on the circuit breaker test
form, which is included with the breaker. If measurements exceeds
200%, contact the manufacturer.
Resistance conversion for Temperature
R
conversion
= R
Factory
(1 + (T
Field
- T
Factory
)
r
)
R
conversion
= Resistance correction for temperature based from the
factory resistance measurement.
R
Factory
= Resistance measurement from the factory.
T
Field
= Temperature measurement in the field.
T
Factory
= Temperature measurement from the factory.
r
= Copper resistivity temperature coefficient.
r
= 0.0039 Copper Resistivity Temperature Coefficient / Deg C
r
= 0.002167 Copper Resistivity Temperature Coefficient / Deg F
6.8 MECHANISM CHECK
Make a careful visual inspection of the mechanism for any loose
parts such as bolts, nuts, pins, rings, etc. Check for excessive wear
or damage to the breaker components. Operate the breaker several
times manually and electrically. Check the closing and opening times
to verify that they are in accordance with the limits in Table 4.1.
6.8.1 CLOSURE™ TEST
Introductione:
The CloSure™ Test is a simple yet extremely effective
means to determine and monitor the ability of the mechanism to
close the breaker contacts fully. It provides a quantitative measure
of the extra energy available in terms of over travel in inches to close
the breaker contacts to their full extent. It may be used periodically
to monitor the health of the mechanism.
Gtntral Informatione:
The CloSure™ Test can be performed on all
VR-Series circuit breakers. (Refer to Table 6.1.) If the CloSure™ travel
obtained is as specified, the mechanism performance is satisfactory.
If the CloSure™ travel does not conform as shown in Figure 6.15,
contact Eaton’s Electrical Services & Systems for further information.
(See Step 13).
WARNING
DO NOT ATTEMPT TO INSTALL OR PERFORM MAINTENANCE OR TESTS ON
THE EQUIPMENT WHILE IT IS ENERGIZED. NEVER PUT YOUR HANDS NEAR
THE MECHANISM WHEN THE CIRCUIT BREAKER IS IN THE CHARGED OR
CLOSED POSITION. DEATH OR SEVERE PERSONAL INJURY CAN RESULT
FROM CONTACT WITH ENERGIZED EQUIPMENT. ALWAYS VERIFY THAT
NO VOLTAGE IS PRESENT BEFORE PROCEEDING WITH THE TASK, AND
ALWAYS FOLLOW GENERALLY ACCEPTED SAFETY PROCEDURES.
Figurt 6.5. Status Indicators (“A” shows tht contact status indi-
cation and “B” shows tht spring indication.)
Figurt 6.6. Wrapping Tapt Around Cam
Saftty Prtcautionse:
Read and understand these instructions before
attempting any maintenance, repair or testing on the breaker. The
user is cautioned to observe all recommendations, warnings and
cautions relating to the safety of personnel and equipment.
The recommendations and information contained herein are based
on Eaton Electrical experience and judgment, but should not be
considered to be all-inclusive or covering every application or
circumstance which may arise. If further information is required, you
should consult Eaton’s Electrical Services & Systems.
Ttsting Proctdurtse:
Assuming that the circuit breaker is safely
removed from the switchgear enclosure and positioned in an area
outside the arc fault boundary, follow this procedure to perform the
CloSure™ test. For further instructions on removal of the circuit
breaker from the switchgear, refer to the appropriate section of this
manual.
Sttp 1 -
On the front cover, identify the status indicators. Make sure
the closing spring status indicates “DISCHARGED” and the main
contact indicator shows “OPEN” (Figure 6.5).
Sttp 2 -
Remove the circuit breaker front cover. Be sure to save the
original fasteners for reassembly.
Sttp 3 -
Charge the circuit breaker, close the circuit breaker, then
open the circuit breaker. Alternately depress the Open and Close
clappers a few times to ensure the circuit breaker is completely
discharged.
Sttp 4 -
Cut a piece of one inch wide drafting / masking tape
approximately 8 to 10 inches long.
A
B
Discharged
Open
