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8. CHARACTERISTICS
8 - 3
8.2 Dynamic brake characteristics
POINT
Dynamic brake operates at occurrence of alarm, servo forced stop warning (E6),
and controller forced stop warning (E7), 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 direct drive motor stops when using
forced stop (EM1) frequently in other than emergency.
8.2.1 Dynamic brake operation
(1) Calculation of coasting distance
Fig. 8.2 shows the pattern in which the direct drive motor comes to a stop when the dynamic brake is
operated. Use equation 8.1 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 (2) of this
section.)
V
0
Dynamic brake time constant
OFF
ON
Machine speed
t
e
Time
Forced stop (EM1)
Fig. 8.2 Dynamic brake operation diagram
L
max
60
V
0
J
L
J
M
t
e
1
································································································································(8.1)
L
max
V
O
J
M
J
L
t
e
: Maximum coasting distance·············································································································· [mm][in]
: Machine rapid feed rate······································································································· [mm/min][in/min]
: Direct drive motor inertial moment ··············································································[×10
-4
kg m
2
][oz in
2
]
: Load inertia moment converted into equivalent value on direct drive motor rotor ·····[×10
-4
kg m
2
][oz in
2
]
: Dynamic brake time constant······················································································································[s]
: Delay time of control section ·······················································································································[s]
There is internal relay delay time of about 10ms.