Mitsubishi Electric MELSERVO-J4 Series Instruction Manual page 512

Dynamic brake operation
■Calculation of coasting distance
The following shows the pattern in which the servo motor comes to a stop when the dynamic brake is operated. Use equation
15.1 to calculate an approximate coasting distance to a stop. The dynamic brake time constant  varies with the direct drive
motor and machine operation speeds.
Page 510 Dynamic brake time constant
ON
EM1 (Forced stop 1)
OFF
Machine
speed
V
0
L = • t + τ 1 +
max e
60
L : Maximum coasting distance [mm]
max
V : Machine's fast feed speed [mm/min]
0
J : Moment of inertia of direct drive motor [kg•]
M
J : Load moment of inertia converted into equivalent value on direct drive motor rotor [kg•]
L
: Dynamic brake time constant [s]
t : Delay time of control section (There is internal relay delay time of about 10 ms.) [s]
e
■Dynamic brake time constant
The following shows necessary dynamic brake time constant  for equation 15.1.
30
25
002
20
15
10
5
0
0
100 200
Direct drive motor speed [r/min]
TM-RFM_C20
60
50
012
40
30
20
10
0
0 100 200
Direct drive motor speed [r/min]
TM-RFM_G20
15 USING A DIRECT DRIVE MOTOR
510
15.4 Characteristics
V
0
t
e
J
L
·········(15.1)
J
M
004
006
300 400 500
048
072
300 400 500
Dynamic brake
time constant
Time
70
60
018
50
006
40
30
20
10
0
0
100 200 300
Direct drive motor speed [r/min]
TM-RFM_E20
80
040
70
60
50
40
30
240
20
10
0
0
50 100
Direct drive motor speed [r/min]
TM-RFM_J10
012
400 500
120
150 200