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9.CHARACTERISTICS
9-4 Dynamic brake characteristics
When an alarm, emergency stop or power failure occurs, the dynamic brake is operated to bring
the servo motor to a sudden stop. Fig. 9-5 shows the pattern in which the servo motor comes to a
stop when the dynamic brake is operated. Use Equation 9-3 to calculate an approximate coasting
distance to a stop. The dynamic brake time constant τ varies with the servo motor and machine
operation speeds as indicated in Table 9-3 and as shown in Fig. 9-6 to Fig. 9-12.
Emergency stop (EMG)
Machine speed
V
o
te + τ (1 +
L
=
•
max
60
Lmax : Maximum coasting distance
Vo
: Machine rapid feedrate
JM
: Servo motor inertial moment
JL
: Load inertia moment converted into equivalent value
on servo motor shaft
τ
: Brake time constant (Fig. 9-6 to 9-12
te
: Delay time of control section (Fig. 9-5)
(There is internal relay delay time of about 30ms.)
0.02
0.018
0.016
0.014
0.012
0.01
0.008
0.006
0.004
0.002
0
0
500 1000 1500 2000 2500 3000
Fig. 9-5 HC-MF Dynamic Brake
Time Constant
ON
OFF
V
0
Fig. 9-4 Dynamic Brake Operation Diagram
J
L
.................................................... (9-3)
)
J
M
23
73
053
43
13
Speed [r/min]
Time constant τ
t
e
Table 9-3)
•
0.04
0.035
0.03
0.025
0.02
0.015
0.01
0.005
0
0
Fig. 9-6 HC-SF1000r/min Dynamic
9– 10
Time
[mm/min][in/min]
[kg
cm
•
[kg
cm
•
121
201
301
81
50
500
1000
Speed [r/min]
Brake Time Constant
[mm][in]
2
][oz
in
2
]
•
2
2
][oz
in
]
•
[s]
[s]
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