Warner Electric FB-375, 475, 650 - Manual (Page 8)

8 Warner Electric • 800-825-9050 P-237 • 819-0289
Check No. 2
A step is machined on the O.D. of the brake
magnet where the armature and magnet meet.
This step is equal to the friction material
thickness. When this step is completely covered
by the armature with the brake engaged, the brake
is worn out and should be replaced.
Magnet worn to step
New
Check No. 2
Worn out
After completing an inspection with the
machine turned off, cycle it several times. If
the Electrically Released Brake stopping time has
more than doubled since the original set-up, this
also indicates the brake is worn out and should
be replaced.
Foreign Materials: If units are used on
machinery where fine, abrasive dust, chips
or grit are dispelled into the atmosphere, a
protective screen over the unit may be
necessary.
Where units are used near gear
boxes or transmissions requiring frequent
lubrication’s, means should be provided to
protect the friction surfaces from oil and
great to prevent serious loss of torque by
reducing the coefficient of friction and
swelling the friction material. Oil and grease
accidentally reaching the friction surfaces may be
removed by wiping with a rag dampened with a
suitable cleaner, which leaves no residue. In
performing this operation, do not drench the
friction material. If the friction material has been
saturated with oil or grease, no amount of
cleaning will be completely effective. Once such
a unit has been placed back in service, heat will
cause the oil to be boiled to the surface
resulting in further torque loss.
The drive pins should be kept free of foreign
materials to ensure proper function of the brake.
Fails to Release: If the Electrically Released
Brake does not release completely, make the
following checks:
1. Check that the electrical connections
(polarity) between the brake coil and the power
supply are correct for the power supply being
used (refer to Step 4, page 6).
2. Connect a DC voltmeter across the brake
terminals. (Do not disconnect the leads to the
terminals.) The voltmeter should indicate a
voltage in the range of 75 to 110 volts.
3. The above checks are normally sufficient.
Further checks may be made by checking the
brake coil resistance.
a. Turn off the power to the brake.
b. Disconnect one lead from the coil to make
sure the circuit is open.
c. Connect an ohmmeter across the brake
terminals. The resistance should be as
shown:
24V Coil Resistance 90V Coil Resistance
Brake Size at 20°C (±10%) at 20°C (±10%)
FB-375 29 447
FB-475 22 310
FB-650 16 235
A very high or infinite resistance reading would
indicate an open coil. A very low resistance would
indicate a shorted coil. In either case, the unit
should be replaced.
Wear Pattern: Wear grooves appear on the
friction surfaces. This is a normal wear condition,
and does not impair functioning of the unit. Never
machine the friction surfaces to remove grooves or
score marks resulting from normal wear.
OK