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)

Emergency stop(EMG) ONOFF

Lmax

Lmax

Vo

JM

JL

te

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

V0

 

Time constant

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Machine speed

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

te

 

 

Time

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig. 12.4 Dynamic brake operation diagram

 

 

 

 

V0

 

te

 

1

JL

 

 

.......................................................................................................................

 

 

 

(12.2)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

60

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

JM

 

 

 

 

 

 

 

 

 

 

 

: Maximum coasting distance

 

 

[mm][in]

: Machine rapid feedrate

 

[mm/min][in/min]

: Servo motor inertial moment

 

[kg cm2][oz in2]

: Load inertia moment converted into equivalent value on servo motor shaft

[kg cm2][oz in2]

: Brake time constant (Fig. 12.5)

 

 

[s]

: Delay time of control section (Fig. 12.4)

 

 

[s]

(There is internal relay delay time of about 30ms.)

 

 

 

 

12 - 4

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Image 191
Mitsubishi Electronics MR-J2S- A 12.2, Mmin, Mm/minin/min, Kg cm2oz in2, There is internal relay delay time of about 30ms