SMC Networks LECSB Series, Руководство по эксплуатации

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11 - 5
11. CHARACTERISTICS
11.3 Dynamic brake characteristics
POINT
Dynamic brake operates at occurrence of alarm, servo emergency stop warning
(AL.E6) 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 inertia moment ratio is 1000 time while decelerating from
rated speed to a stop with frequency of once in 10 minutes.
Be sure to make emergency stop (EMG) valid after servo motor stops when
using emergency stop (EMG) frequently in other than emergency.
11.3.1 Dynamic brake operation
(1) Calculation of coasting distance
Fig. 11.3 shows the pattern in which the servo motor comes to a stop when the dynamic brake is operated.
Use Equation 11.2 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) (a), (b) in this section.)
V
0
OFF
ON
Machine speed
t
e
Time
Emergency stop (EMG)
Dynamic brake
time constant
Fig. 11.3 Dynamic brake operation diagram
L
max
60
V
0
J
L
J
M
t
e 1
...................................................................................................................... (11.2)
L
max
: Maximum coasting distance .................................................................................................... [mm][in]
Vo : Machine rapid feed rate .............................................................................................. [mm/min][in/min]
J
M
: Servo motor inertial moment ..................................................................................... [kg cm 2 ][oz in 2 ]
J
L
: Load inertia moment converted into equivalent value on servo motor shaft ............ [kg cm
2
][oz in
2
]
: Dynamic brake time constant ........................................................................................................... [s]
t
e
: Delay time of control section ............................................................................................................. [s]
For 7kW or lower servo, there is internal relay delay time of about 10ms. For 11k to 22kW servo,
there is delay caused by magnetic contactor built into the external dynamic brake (about 50ms)
and delay caused by the external relay.