Warner Electric Primary Brake Pin Drive Armature PB-825, PB-1000, PB-1225, PB-1525 Motor Brake and Spline Drive MB-825, MB-1000, MB-1225 Pin Drive - Manual (Page 11)

11 Warner Electric • 800-825-9050 P-208 • 819-0367
Foreign Materials: If units are used on
machinery where fine, abrasive dust, chips or grit
are dispelled into the atmosphere, shielding of
the brake may be necessary if maximum life is to
be obtained.
Where units are used near gear boxes or
transmissions requiring frequent lubrication,
means should be provided to protect the friction
surfaces from oil and grease to prevent serious
loss of torque.
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 materials have 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
boil to the surface, resulting in further torque loss.
Torque Loss: If a brake or clutch slips or loses
torque completely, the initial check should be the
input voltage to the magnet as follows:
90-Volt Series: Connect a DC voltmeter with a
range of 0-100 or more directly across the
magnet terminals. With the power on and the
potentiometer turned up, a normal reading is 90
volts, although 85 to 95 is satisfactory. The
reading should drop as the potentiometer
control is adjusted counterclockwise.
24-Volt Series: Use a DC voltmeter with a
range of 0-30 volts or more. A normal reading
is approximately 22-26 volts.
6-Volt Series: Use a DC voltmeter of
approximately 0-15 volt range. A normal
reading is from 5.5 to 6.5 volts.
The above checks normally are sufficient.
Further checks may be made as follows: a
low range ammeter, when connected in series
with one magnet lead, will normally indicate
approximately .40 amperes for the 90 volt
units, 1.0 ampere for the 24 volt, and 3.5
amperes for the 6 volt series. These readings
are with the power on and the potentiometer
control in the maximum position.
Ohmmeter checks should be made with the
power off and the circuit open (to be certain,
disconnect one lead to the magnet). Average
resistance for the 90 volt series is 220 ohms;
for the 24 volt, 20 ohms; and for the 6 volt
series, 1.5 ohms. A very high or infinite
resistance reading would indicate an open coil.
If the above checks indicate that the proper
voltage and current is being supplied to the
magnet, mechanical parts should be checked
to assure that they are in good operating
condition and properly installed.