Lenze MGXQK DC motors - Manual (Page 16)

16
Checking and replacing carbon brushes
1. For MGXRK series:
Dismantle blower hood and tightening
strap.
For MGXQU series:
Dismantle cover sheets at the B--side
endshield.
2. Loosen carbon abrasion inside the motor
using a brush and suck off.
Do not blow out, because the dust may be
blown inside the motor and in the winding
heads.
3. Take off spring of the brush holder, take out
carbon brushes and measure the length of
the brushes:
-- The carbon brushes are marked with
letters. The lower edge of the letters is
the wear limit.
-- If this limit is almost reached, always
replace the carbon brushes in sets.
Only use genuine carbon brushes or
those approved by the manufacturer,
otherwise the commutation and brush
life are endangered (for orders see
chapter 8.2).
4. Insert carbon brushes such that they easily
slide in the brush holders.
Place the wires such that the carbons can
slide without being obstructed, when they
are shortened due to wear.
5. To ensure a good electrial contact between
carbon brushes and collector, grind the
carbon brushes such that they are adapted
to the collector diameter before the motor
is commissioned:
-- For motors which have free access to
the shaft ends and where the rotors can
easily be rotated by hand (fig. 4,
sketch 1):
Fix abrasive paper or abrasive cloth of
grain 180 or hold by hand.
Insert the new carbon brushes and
place spring of the brush holder on the
carbon brushes.
Then turn the rotor of the motor to both
sides until the contact surface of the
carbon brushes has completely adapted
to the running surface diameter of the
collector.
-- For heavy motors which are difficult to
move and those motors the shafts ends
of which are not accessible, the carbon
brushes of each pole must be ground
separately (fig. 4, sketch 2):
Lay a strip of abrasive paper or abrasive
cloth of grind 180, the length of which
corresponds to the length of the
collector running surface, between the
running surface and the brush holders of
a pole.
Insert the new carbon brushes and
place the spring on the carbon brushes.
By moving the abrasive paper under the
carbon brushes to both sides along the
collector shape, grind all carbon
brushes of a pole at the same time.
sketch 1 sketch 2
K33.0005
Fig. 4: Grinding of carbon brushes
6. Take carbon brushes out of the brush
holders. Carefully remove grinding and
carbon dust.
7. Insert carbon brushes again.
8. After disconnecting and turning the brush
yoke:
-- Set ”neutral zone” again. For this, the
mark at the brush yoke and the
endshield must exactly coincide.
Reconnect brush yoke.
9. For MGXRK series:
Reassemble tightening strap and blower
hood.
For MGXQU series:
Reassemble cover sheets.
The motor is now ready to operate again.
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