Mitsubishi Electric MELSERVO-J3W Series, Instruction Manual

Page: 181 / 500

10. CHARACTERISTICS
10 - 4
10.3 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.
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 make forced stop (EM1) valid after servo motor stops when using forced
stop (EM1) frequently in other than emergency.
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 varies with the servo motor and machine operation speeds. (Refer to (2) of this section.)
V
0
OFF
ON
Machine speed
t
e
Time
Forced stop (EM1)
Dynamic brake
time constant
Fig. 10.3 Dynamic brake operation diagram
L
max
60
V
0
J
L
J
M
t
e
1
......................................................................................................................(10.2)
L
max
: Maximum coasting distance .................................................................................................... [mm][in]
Vo : Machine rapid feed rate ..............................................................................................[mm/min][in/min]
J
M
: Servo motor inertial moment..............................................................................[×10
-4
kg m
2
][oz in
2
]
J
L
: Load inertia moment converted into equivalent value on servo motor shaft ....[×10
-4
kg m
2
][oz in
2
]
: Dynamic brake time constant ............................................................................................................[s]
t
e
: Delay time of control section............................................................................................................. [s]
There is internal relay delay time of about 10ms.