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Instruction Book IB019009EN November 2017 www.eaton.com
AK-2-25, AK-2A-25, & AK-3A-25 LV-VSR
Breaker-To-Motor Starter Conversion
SECONDARY CIRCUIT:
WARNING
BEFORE PERFORMING SECONDARY INSULATION CHECK PLACE A JUMPER
ON THE CONTACTOR COIL ASSEMBLY POINTS (A) TO (B). FAILURE TO DO
SO MAY RESULT IN DAMAGE TO THE SOLID STATE RECTIFIER IN THE COIL
ASSEMBLY.
1. Ensure that a jumper is placed on contactor coil assembly
points (A) to (B).
2. Connect all points of the secondary disconnect pins with a
shorting wire.
3. Connect Current Transformers with a shorting wire and
connect them to the frame.
4. Connect the high potential lead of the test machine to the
secondary block.
5. Ground the LV-VSR frame.
6. Starting with zero, increase the voltage to 1200 Vac RMS, 60
Hz. Maintain the voltage for one minute.
7. Successful withstand indicates satisfactory insulation
strength of the secondary control circuit.
8. Remove ALL shorting wire on Current Transformers and
secondary block before placing unit back into service.
9. Remove jumper from contactor coil assembly points (A) to
(B).
WARNING
FAILURE TO REMOVE ALL SHORTING WIRE FROM CURRENT
TRANSFORMERS AND SECONDARY CONNECTIONS MAY CAUSE INJURIES
AND EQUIPMENT DAMAGE.
6.7 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 LV-VSR components. Operate the LV-VSR several
times electrically to verify operation.
6.8 LUBRICATION
All parts that require lubrication have been lubricated during the
assembly with molybdenum disulphide grease. Cutler-Hammer
No. 53701QB. Over a period of time, this lubricant may be pushed
out of the way or degrade. Proper lubrication at regular intervals is
essential for maintaining the reliable performance of the mechanism.
The LV-VSR should be re-lubricated once a year. The locations shown
in Figure 6-2 should be lubricated with a drop of non-synthetic light
machine oil. After lubrication, operate the LV-VSR several times
manually and electrically.
6.9 PRIMARY CIRCUIT RESISTANCE CHECK
Since the main contacts are inside the vacuum chamber they remain
clean and require no maintenance at any time.
The dc resistance of the primary circuit may be calculated by
measuring the voltage drop across the circuit. To check the primary
circuit resistance remove the LV-VSR from the switchgear, close the
LV-VSR and pass at least 10A dc through one of the breaker’s poles.
Measure the voltage drop across the primary contacts and calculate
the resistance. Repeat for the remaining two poles.
6.10 MAGNET OPERATING RANGE
If the magnet chatters, look for mechanical interference that
prevents the magnet itself may be misaligned. The magnet gap can
be seen from the left and right sides with the help of a flashlight.
A screwdriver inserted into one of the long slots can be used as
a lever to put a corrective set into the mounting plate around the
magnet. It should not be necessary to do this unless the contactor
has been damaged and it can be seen that the armature does not fit
against the magnet. A poor magnet to armature fit usually produces
a high dropout voltage and/or chatter.
Mechanical interference can be produced by various incorrect
adjustments. Two specific points to check are:
A. Armature travel incorrect, causing the contact springs to be
compressed into a solid, non-resilient “tube” that stops the
crossbar rigidly. Refer to Eaton’s Electrical Services and Systems for
assistance.
B. The auxiliary contact mounting brackets are mis-adjusted, so that
a contact plunger bottoms solidly before the magnet seals. When
the contactor is fully sealed closed, there should still be a small
amount of travel remaining for the plungers.
L63 Auxiliary Contact Adjustment
The normal .34 inch pretravel gap for the L63 auxiliary contact
(normally-closed) is important. If the gap is too big, the “hold”
winding of the operator coil will not be inserted as the contactor
closes, and the pickup winding will burn out, because the pickup
winding is only intermittenly rated. If the gap is too small, the
hold winding will be inserted too soon, reducing the force to
“hold” before the contactor is closed, and producing an oscillation
like a doorbell. In a particular contactor, the .34 gap may need
slight adjustment to avoid these problems. The key is not the
measurement, but the performance of the magnet.
The auxiliary contacts are not as critical. In the open position, their
plungers may rest lightly against the operating arm, or may have a
small clearance.
However, neither of the auxiliary contact polungers should bottom
solidly in the closed contactor position, as discussed under MAGNET
OPERATING RANGE. If required, the auxiliaries can be adjusted by
reseting their mounting brackets in their slotted holes. Adjust the
L63 by loosening the two slotted hexagonal washer head screws
that hold the L63 mounting bracket, repositioning and tightening.
These bracket mounting screws are accessible from the top side of
the contactor and are recognized by the slotted holes under their
heads.
