Warner Electric PB-650 Pin Drive - Manual (Page 15)

15 Warner Electric • 800-825-9050 819-0485
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 or field as
follows:
90-Volt Series: Connect a DC voltmeter with
a range of 0-100 or more directly across the
magnet or field 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.