Dynamic Brake Operation - Mitsubishi Electric MR-JE-_A Instruction Manual

10. CHARACTERISTICS

10.3.1 Dynamic brake operation

(1) Calculation of coasting distance
Fig. 10.3 shows the pattern in which the servo motor comes to a stop when the dynamic brake is
operated. Use equation 10.2 to calculate an approximate coasting distance to a stop. The dynamic
brake time constant τ varies with the servo motor and machine operation speeds. (Refer to (2) in this
section.)
A working part generally has a friction force. Therefore, actual coasting distance will be shorter than a
maximum coasting distance calculated with the following equation.
V
0
t +
L = •
max
e
60
L : Maximum coasting distance ······················································································ [mm]
max
V : Machine's fast feed speed ····················································································· [mm/min]
0
J : Moment of inertia of the servo motor ································································· [× 10
M
J : Load moment of inertia converted into equivalent value on servo motor shaft ·············· [× 10
L
τ: Dynamic brake time constant ···························································································· [s]
t : Delay time of control section ···························································································· [s]
e
There is internal relay delay time of about 10 ms.
(2) Dynamic brake time constant
The following shows necessary dynamic brake time constant τ for equation 10.2.
EM1 (Forced stop 1)
Fig. 10.3 Dynamic brake operation diagram
J
1 + L
··························································································· (10.2)
J
M
60
50
40
30
20
10
0
0 1000 2000 3000 4000 5000 6000
Speed [r/min]
HG-KN series
ON
OFF
V
0
Machine speed
200
180
73
160
140
120
23
100
80
43
60
13
40
20
10 - 5
Dynamic brake
time constant τ
t
e
102
202
0
0 500 1000 1500 2000 2500 3000
Speed [r/min]
HG-SN series
Time
-4 2
kg•m ]
-4 2
kg•m ]
52
302
152