Rockwell Automation 808 SPEED SWITCHES - Manual (Page 2)

SPEED SENSING AND DIRECTION OF ROTATION
in these applications,
the device with either normally open or normally closed con-
tacts can be used depending upon the requirements of the cir-
cuit. For example, when connected to an alarm circuit, the
speed switch can be used to sense belt breakage. The speed
switch can also be used to sequence conveyors where it is
essential for one conveyor to be in motion or up to a preselected
speed before a second conveyor is started. See Figure 3. The
switch will also indicate thedirectional movement of a conveyor
by monitoring the rotation of a suitable driven shaft. See Figure 4.
PRECAUTIONS
The shaft of the speed switch should be driven
at the highest available speed within the maximum speed
specified in Table 1 below. The continuous driven speed should
be at least 2 times the speed at which the contacts are set to
operate. This will provide high contact force and reduce the
possibility of contact “chatter” and erratic operation of the
switch.
TYPICAL CONVEYOR SEQUENCING CIRCUIT
M2 starts automati-
cally when Ml comes up to speed.
NOTE:
See applicable standards, codes, and laws for all
applications.
L1
Stop
Rev.
FIGURE 3
TYPICAL DIRECTION OF ROTATION CIRCUIT
NOTE:
See applicable standards, codes, and laws for all
applications.
L1 L 2
FIGURE 4
TABLE 1 S P E E D S W I T C H C H A R A C T E R I S T I C S I
Styles with Normally Open Contacts J M
Styles with Normally Closed Contacts K R
Contact Operating Speed Range (RPM) - 8 0 50-1000
Maximum Shaft Ooeratina Soeed (RPM) 1200 2000
Maximum Driving Torque (Inch-Pounds) 3.5 3.5
Temperature Rise (Degrees F)
120 140
q
When mounted with
adjustment screws not at the
same level,
minimum adjustable speed IS 20 R
PM
IMPORTANT: Do not run the speed switch at any time at a speed higher than the
indicated maximum speed since permanent damage to the switch may result.
2 CONTACT RATING I
I AC NEMA Rating Oesignation 8600
I
2
COUPLING Speed switch coupling must be positive to avoid
slippage. A direct flexible coupling is best. This type of coupling
also minimizes bearing wear on both the speed switch and the
driven shaft of the machine due to the unavoidable difficulties
of accurate alignment of separate shafts. Gears, chain, or
timing belt can be used successfully. A rigid coupling should
not be used. (See Table 1 for driving torque and maximum
speed specifications.)
PRECAUTIONS
It is important not to overload the shaft of the
speed switch or shortened bearing life may result. Radial loads
on the NEMA Type 1,4, 13 speed switch should not exceed 50
pounds and axial loads (thrust loads) should not exceed 20
pounds. Radial loads on the NEMA Type 7 & 9 speed switch
should not exceed 25 pounds and axial loads (thrust loads)
should not exceed 20 pounds.
In speed sensing or direction of motion applications, a timing
or V belt may be used. Proper belt tension must be maintained
to keep slippage at a minimum. The maximum belt tension must
not exceed 25 pounds.
SPEED SWITCH WITH COVER REMOVED
Clockwise Shaft
Rotation
(Front View)
Counterclockwise
Shaft Rotation
(Front View)
Terminal Screw
Adjustment Screw
Terminal Screw
Rear View
ADJUSTMENT
The speed switch is easily adjusted by means of
two external adjusting screws one for each set of contacts.
One screw controls clockwise rotation, the other counterclock-
wise. Use
hex wrench.
Prior to adjustment run the speed switch at operating speed
until the switch reaches its normal operating temperature.
PLUGGING Turn adjusting screw(s) in or out to achieve
stopping at zero speed. Adjust both screws when circuit requires
switch to be wired for plug stopping in both directions.
Adjustment depends upon the speed of the machine. Improper
adjustment will cause the machine to either:
1. Coast to a stop, caused by not providing enough counter-
torque;
2. Permit a back-spin (shaft rotating in opposite direction),
caused by providing too much counter-torque.
Adjustment of the speed switch must be made between these
two conditions to achieve zero shaft speed.
ANTIPLUGGING
Turn adjusting screw(s) out measuring
from end of hex socket head toenclosure (lowest speed setting).
When circuit requires switch to be wired for antiplugging control
in both directions, both screws will require adjusting.
1. Turning screw(s) in will permit reverse energization to be
applied manually or automatically at a higher shaft speed.
2. Adjust to desired speed as determined by trial runs.