12 - 4
12. CHARACTERISTICS
12.3 Dynamic brake characteristics
When an alarm, emergency stop or power failure occurs, the dynamic brake is operated to bring the servo
motor to a sudden stop. Fig. 12.4 shows the pattern in which the servo motor comes to a stop when the
dynamic brake is operated. Use Equation 12.2 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
Fig. 12.5)
V0Time constant
Emergency stop(EMG) OFF
ON
Machine speed
teTime
Fig. 12.4 Dynamic brake operation diagram
Lmax 60
V0JL
JM
te1.......................................................................................................................(12.2)
Lmax : Maximum coasting distance .................................................................................................[mm][in]
Vo : Machine rapid feedrate......................................................................................... [mm/min][in/min]
JM: Servo motor inertial moment................................................................................. [kg cm2][oz in2]
JL: Load inertia moment converted into equivalent value on servo motor shaft .....[kg cm2][oz in2]
: Brake time constant (Fig. 12.5) ......................................................................................................[s]
te: Delay time of control section (Fig. 12.4)......................................................................................... [s]
(There is internal relay delay time of about 30ms.)