10 - 5
10. CHARACTERISTICS
10.3 Dynamic brake characteristics
POINT
The dynamic brake is operated when an alarm occurs, a servo forced stop
warning occurs, or the power turns off. The dynamic break is a function for
emergency stops. Do not use this function for normal stops.
The criteria for the number of times the dynamic break is used is 1000 times,
in the condition that the machine with recommended load to motor inertia
moment ratio or less, stops from the rated speed in a frequency of once per
10 minutes.
When using the forced stop (EM1) frequently for other than emergencies, be
sure to turn off the forced stop (EM1) after the servo motor stops.
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 paragraph (2) of this
section.)
OFF
ON
Machine speed
V
0
t
e
Time constant
Time
Forced stop (EM1)
Fig. 10.3 Dynamic brake operation diagram
L
max
=
V
0
60
t
e
+
1+
J
L
J
M
................................................................................................................... (10.2)
L
max
: Maximum coasting distance ..................................................................................... [mm][in]
V
0
: Machine rapid feed rate.............................................................................. [mm/min][in/min]
J
M
: Servo motor inertial moment ................................................................... [kg cm
2
][oz cm
2
]
J
L
: Load inertia moment converted into equivalent value on servo motor shaft
................................................................................................................. [kg cm
2
][oz cm
2
]
: Brake time constant ........................................................................................................... [s]
t
e
: Delay time of control section ............................................................................................. [s]
There is internal relay delay of about 10ms.
