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11. CHARACTERISTICS
11.2 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. 11.2 shows the pattern in which the servo motor comes to a stop when the
dynamic brake is operated. Use Equation 11.1 to calculate an approximate coasting distance to a stop. The
dynamic brake time constant
11.3.)
Emergency stop (EMG)
Vo
Lmax =
te
60
L max : Maximum coasting distance
Vo
: Machine rapid feedrate
J
: Servo motor inertial moment
M
J
: Load inertia moment converted into equivalent value on servo motor shaft
L
: Brake time constant (Fig. 11.3)
t
: Delay time of control section (Fig. 11.2)
e
(There is internal relay delay time of about 30ms.)
Use the dynamic brake at the load inertia moment indicated in the following table. If the load inertia
moment is higher than this value, the built-in dynamic brake may burn. If there is a possibility that the
load inertia moment may exceed the value, contact Mitsubishi.
varies with the servo motor and machine operation speeds. (Refer to Fig.
ON
OFF
Machine speed
V
0
Fig. 11.2 Dynamic Brake Operation Diagram
J
L
1
J
M
0.0025
0.002
HC-AQ0135
0.0015
0.001
0.0005
0
0
100
400
700 1000 1300 1600
Fig. 11.3 Dynamic Brake Time Constant
Servo Amplifier
MR-J2-03A5
Time constant
t
e
HC-AQ0335
1900 2200 2500 2800 3000
Speed [r/min]
Load Inertia Moment Ratio [times]
100
11 - 2
Time
[mm/min][in/min]
[kg cm
[kg cm
HC-AQ0235
(11.1)
[mm][in]
][oz in
]
2
2
][oz in
]
2
2
[s]
[s]
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