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APPENDIX
App. 5.10 Coasting distance of electromagnetic brake
At an emergency stop, the servo motor with an electromagnetic brake stops as the following diagram. Here,
the maximum coasting distance (during fast feed) L
figure and can be calculated approximately with equation 5.30. The effect of the load torque is greater near
the stopping area. When the load torque is large, the servo motor will stop faster than the value obtained in
the equation.
V
t
0
t
+ t
+
3
L
=
•
max
1
2
60
2
L
: Maximum coasting distance [mm]
max
V
: Machine's fast feed speed [mm/min]
0
t
: Delay time of control section [s]
1
t
: Braking delay time (Note) [s]
2
t
: Braking time [s]
3
(J
+ J
) • N
L
M
0
t
=
3
4
9.55 • 10
• (T
+ 0.8 • T
L
J
: Load moment of inertia converted into equivalent value on servo motor shaft (Note) [× 10
L
J
: Servo motor rotor's inertia moment [× 10
M
N
: Servo motor speed during fast feed [r/min]
0
T
: Load torque converted into equivalent value on servo motor shaft [N•m]
L
T
: Brake static friction torque (Note) [N•m]
B
Note. Refer to the chapter of the servo motor series for t
App. 5.11 Equation for calculating the electromagnetic brake workload
Calculate the brake workload Eb [J] at an emergency stop with the following equation.
2
(J
+ J
) • N
-4
Eb =
M
L
• 10
182
N: Servo motor speed [r/min]
J
: Servo motor rotor's inertia moment [× 10
M
J
: Load moment of inertia converted into equivalent value on servo motor shaft [× 10
L
Emergency stop
Brake current
Machine speed
······································································································· (5.30)
)
B
-4
kg•m
and T
2
-4
kg•m
will be the area shown with the diagonal line in the
max
t
t
1
2
V
0
2
]
. J
is moment of inertia of the machine at the servo motor shaft.
B
L
2
]
App. - 27
t
3
-4
kg•m
2
]
-4
2
kg•m
]
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