Mitsubishi Electric MELSERVO-J4 series, Instruction Manual

Page: 512 / 646

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