Mitsubishi Electric MELSERVO-J3W Series, Instruction Manual

Page: 395 / 500

14. USING A DIRECT DRIVE MOTOR
14 - 62
14.7.2 Dynamic brake characteristics
POINT
Dynamic brake operates at occurrence of alarm, Servo forced stop warning (E6.1),
and Controller forced stop warning (E7.1), and when power is turned off. Do not
use dynamic brake to stop in a normal operation as it is the function to stop in
emergency.
Maximum usage time of dynamic brake for a machine operating under
recommended load to motor inertia ratio is 1000 time while decelerating from rated
speed to a stop with frequency of once in 10 minutes.
Be sure to enable Forced stop (EM1) after the direct drive motor stops when using
Forced stop (EM1) frequently in other than emergency.
(1) Dynamic brake operation
(a) Calculation of coasting distance
Fig. 14.3 shows the pattern in which the servo motor comes to a stop when the dynamic brake is
operated. Use equation 14.1 to calculate an approximate coasting distance to a stop. The dynamic
brake time constant varies with the direct drive motor and machine operation speeds. (Refer to (1) (b)
of this section.)
V
0
Dynamic brake time constant
OFF
ON
Machine speed
t
e
Time
Forced stop (EM1)
Fig. 14.3 Dynamic brake operation diagram
L
max
60
V
0
J
L
J
M
t
e
1
......................................................................................................................(14.1)
L
max
: Maximum coasting distance .................................................................................................... [mm][in]
Vo : Machine's fast feed speed ..........................................................................................[mm/min][in/min]
J
M
: direct drive motor inertia moment ....................................................................[ 10
-4
kg m
2
][oz in
2
]
J
L
: Load moment of inertia converted into equivalent value on direct drive motor rotor
··························································································································[ 10
-4
kg m
2
][oz in
2
]
: Dynamic brake time constant ............................................................................................................[s]
t
e
: Delay time of control section (Note)...................................................................................................[s]
Note. There is internal relay delay time of about 10ms.