MITSUBISHI ELECTRIC MR-J2S- CP - Manual (Page 253)

13 - 4
13. CHARACTERISTICS
13.3 Dynamic brake characteristics
13.3.1 Dynamic brake operation
(1) Calculation of coasting distance
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 (2) of this
section.)
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]
V
0
: Machine rapid feed rate ........................................................................................ [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]
(There is internal relay delay time of about 30ms.)
(2) Dynamic brake time constant
The following shows necessary dynamic brake time constant for the equations (13.2).
0
14
16
2
4
8
10
6
12
0 500 1000 1500 2000 2500 3000
13
73
23
43
053
Speed [r/min]
T
im
e c
on
sta
nt
[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]
T
im
e const
ant
[
s]
a. HC-KFS series b. HC-MFS series