Mitsubishi Electric MELSERVO MR-J3-xT, Instruction Manual

Page: 350 / 471

13 - 6
13 CHARACTERISTICS
13.3 Dynamic brake characteristics
Fig. 13.3 shows the pattern in which the servo motor comes to a stop when the dynamic brake is operated.
Use Equation 13.2 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. 13.4, 13.5)
V
0
Time constant
Forced stop(EMG)
OFF
ON
Machine speed
t
e
Time
Fig. 13.3 Dynamic brake operation diagram
L
max
60
V
0
J
L
J
M
t
e
1
....................................................................................................................... (13.2)
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
0 1000 2000
5
10
15
20
25
3000 4000 5000 6000
43
053
13
23 73
T
im
e c
on
sta
nt
[m
s]
0
0 1000 2000
5
10
15
20
25
3000 4000 5000 6000
43
053
13
23
73
Speed [r/min]
T
im
e const
ant
[m
s]
HF-MP series HF-KP series
Speed [r/min]
T
im
e
co
ns
ta
nt
[m
s]
500 1000 1500 2000
10
20
30
40
50
60
0
0
81
201
121
51
421
301
Speed [r/min]
T
im
e const
ant
[
m
s]
52
500 1000 1500 2000 2500 3000
152
20
40
60
80
100
120
0
0
102
202
502
702
352
HF-SP1000r/min series HF-SP2000r/min series
Fig. 13.4 Dynamic brake time constant