Stearns 500 User Manual

motor terminals as shown, or other
equivalent combinations. If a 230 volt
brake coil is connected as shown in
Figures 5 or 6, the motor can be operated
on either 230 volts or 460 volts with no
adverse effect on brake operation.

1. All Stearns DC coils are single voltage

dual winding. A high current pull-in
winding is initially energized to start the
plunger movement, while a low current
holding winding is momentarily shunted
from the circuit until the plunger has
pulled in. The older design incorporated a
mechanical switch mounted to the
solenoid frame and actuated by an arm
mounted to the plunger to bring the
holding coil into the circuit. In addition,
coils over 48 Vdc have an arc
suppression module in parallel with the
switch contacts to protect the contacts
from arc erosion and suppress EMI. The
polarity of the incoming power supply is
immaterial with the mechanical switch.
The new electronic switch design
incorporates an electronic timing circuit to
allow the plunger to pull in, then
electrically switch to the holding winding.
Polarity of the power supply to the
electronic switch and coil must be
maintained. Refer to Figure 7 for proper
wiring.

Caution! Never use a series resistor to
drop power supply voltage to the coil as
brake malfunction will result.

2. Due to high initial current demands of a

DC solenoid, a separate DC power
source of adequate current capacity is
usually required.

Caution! For electrical release of brake,
apply full rated coil voltage instantly. Do
not increase voltage slowly.

These series of brakes are factory set for
nominal rated static torque which is
maximum torque. Torque may be decreased
for increased stopping time, see Table 1.
The torque on the 1-1/2 lb-ft brake may not
be reduced.

Note 1: Torque adjust screws on older
brakes are 1/4” shorter than shown in Table
1. For replacement screws use part number
8-009-501-00 and specify 2” length needed
or use part number 8-009-503-00 and
specify 2-3/4” length needed, based on
series and torque from Table.

Note 2: Both adjustment screws (11), Figure
8, must be turned equal amounts
counterclockwise to decrease torque.

Warning! Any mechanism or load held in
position by the brake should be secured to
prevent possible injury to personnel or
damage to equipment before any
disassembly of the brake is attempted or
before the manual release knob is operated
on the brake.

Observe all cautions listed at the beginning
of this manual before attempting to service
brake.

A. Adjustment for friction disc wear
(see Table 2 and Figure 8)

1. Manually lift solenoid plunger to maximum

travel. Depress and allow solenoid
plunger to snap out several times.
Measure solenoid air gap between mating
ground surfaces of solenoid frame and
solenoid plunger. (On vertically mounted
brakes, it will be necessary to push
solenoid plunger into solenoid frame to

3 and 4

2

1

High voltage

–

2 and 4

1 and 3

Low voltage

Figure 4

Figure 5

Figure 6

Figure 7

*Arc suppression used for coil above 48 Vdc.

**Follow polarity for switch to operate.

Electronic Switch** 

(New Style)

Mechanical Switch 

(Old Style)

1-7/8

2-3/4

16

3

20

55,000
55,400
57,500

7/8

2

16

3

15

57,500

1

2

16

3

10

57,500

1-7/8

2-3/4

16

3

25

55,000
55,200
55,400
57,500

1

2

16

3

3, 6, 10 & 15

55,000
55,200
55,400

1-1/8

2

16

3

1.5

55,000

1-27/32

2-3/4

16

3

15

55,500
55,300

7/8

2

12

4

3, 6 & 10

55,300

1

2

12

4

1.5

55,500

Figure 8

–
–

9/16”
9/16”
9/16”

13/32”

1/2”
1/2”

9/16”

–

13/32”

1/2”

9/16”
9/16”
9/16”

1.5; 3

6

10
15

20; 25

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