3 dynamic brake characteristics, Characteristics – MITSUBISHI ELECTRIC MELSERVO MR-J2S- A User Manual
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12 - 5
12. CHARACTERISTICS
12.3 Dynamic brake characteristics
Fig. 12.6 shows the pattern in which the servo motor comes to a stop when the dynamic brake is operated.
Use Equation 12.2 to calculate an approximate coasting distance to a stop. The dynamic brake time
constant varies with the servo motor and machine operation speeds. (Refer to Fig. 12.7. Please contact
us for the servo motor not indicated.)
V
0
Time constant
Emergency stop(EMG)
OFF
ON
Machine speed
t
e
Time
Fig. 12.6 Dynamic brake operation diagram
L
max
60
V
0
J
L
J
M
t
e
1
....................................................................................................................... (12.2)
L
max
: Maximum coasting distance .................................................................................................[mm][in]
Vo
: Machine rapid feedrate ......................................................................................... [mm/min][in/min]
J
M
: Servo motor inertial moment................................................................................. [kg cm
2
][oz in
2
]
J
L
: Load inertia moment converted into equivalent value on servo motor shaft..... [kg cm
2
][oz in
2
]
: Brake time constant ........................................................................................................................ [s]
t
e
: Delay time of control section........................................................................................................... [s]
For 7kW or less servo, there is internal relay delay time of about 30ms. For 11kW to 22kW
servo, there is delay time of about 100ms caused by a delay of the external relay and a delay of
the magnetic contactor built in the external dynamic brake.
Speed[r/min]
0
14
16
2
4
8
10
6
12
0
500 1000 1500 2000 2500 3000
13
73
23
43
053
T
im
e
c
o
n
s
ta
n
t
[
m
s
]
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
0.018
0.02
0
500
1000 1500 2000 2500 3000
73
23
43
053
13
Speed [r/min]
Ti
m
e
c
o
nst
ant
[
s
]
a. HC-KFS series
b. HC-MFS series
Fig. 12.7 Dynamic brake time constant 1