15. USING A DIRECT DRIVE MOTOR
15 - 21
15.4.3 Dynamic brake characteristics
CAUTION
The coasting distance is a theoretically calculated value which ignores the
running load such as friction. The calculated value will be longer than the actual
distance. If an enough braking distance is not provided, a moving part may crash
into the stroke end, which is very dangerous. Install the anti-crash mechanism
such as an air brake or an electric/mechanical stopper such as a shock absorber
to reduce the shock of moving parts.
POINT
Do not use dynamic brake to stop in a normal operation as it is the function to
stop in emergency.
For a machine operating at the recommended load to motor inertia ratio or less,
the estimated number of usage times of the dynamic brake is 1000 times while
the machine decelerates from the rated speed to a stop once in 10 minutes.
Be sure to enable EM1 (Forced stop 1) after the direct drive motor stops when
using EM1 (Forced stop 1) frequently in other than emergency.
(1) Dynamic brake operation
(a) Calculation of coasting distance
Fig. 15.3 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
τ
varies with the direct drive motor and machine operation speeds. (Refer to (1)
(b) in this section.)
Dynamic brake
time constant
τ
Time
t
e
V
0
ON
OFF
EM1 (Forced stop 1)
Machine
speed
Fig. 15.3 Dynamic brake operation diagram
L
max
=
60
V
0
•
J
M
t
e
1 + J
L
······················································································ (15.1)
L
max
: Maximum coasting distance ................................................................................................... [mm]
V
0
: Machine's fast feed speed ................................................................................................. [mm/min]
J
M
: Moment of inertia of direct drive motor ....................................................................... [× 10
-4
kg•m
2
]
J
L
: Load moment of inertia converted into equivalent value on direct drive motor rotor .. [× 10
-4
kg•m
2
]
τ
: Dynamic brake time constant .......................................................................................................... [s]
t
e
: Delay time of control section .......................................................................................................... [s]
There is internal relay delay time of about 10 ms
Summary of Contents for MR-J4W2-0303B6
Page 39: ...2 INSTALLATION 2 8 MEMO ...
Page 97: ...4 STARTUP 4 20 MEMO ...
Page 181: ...6 NORMAL GAIN ADJUSTMENT 6 28 MEMO ...
Page 235: ...9 DIMENSIONS 9 6 MEMO ...
Page 245: ...10 CHARACTERISTICS 10 10 MEMO ...
Page 309: ...13 USING STO FUNCTION 13 14 MEMO ...
Page 365: ...15 USING A DIRECT DRIVE MOTOR 15 24 MEMO ...
Page 389: ...16 FULLY CLOSED LOOP SYSTEM 16 24 MEMO ...
Page 461: ...17 APPLICATION OF FUNCTIONS 17 72 MEMO ...
Page 556: ...APPENDIX App 41 ...
Page 585: ...MEMO ...