Dynamic Brake Characteristics - Mitsubishi Electric Melservo-H Series Specifications And Instruction Manual

8. CHARACTERISTICS
When air flows along the outer wall of the enclosure, effective heat exchange will be possible,
because the temperature slope inside and outside the enclosure will be steeper.
(3) Fitting of the servo amplifier
When mounted with the heat sink outside mounting attachment (option), the servo amplifier can
dissipate generated loss directly to the outside of a control box. This method can reduce the heat
dissipation area of the control box since 45 to 55% of the generated loss given in Table 8.1 is dissipated
to the outside of the enclosure. For details of the heat sink outside mounting attachment, refer to
Section 9.1.4.

8.3 Dynamic brake characteristics

When the optional dynamic brake is used, the occurrence of an alarm, emergency stop or a power failure
causes the dynamic brake to be operated to bring the servo motor to a sudden stop. Fig. 8.2 shows the
pattern in which the servo motor comes to a stop when the dynamic brake is operated. Use Equation 8.2
to calculate an approximate coasting distance to a stop. The dynamic brake time constant t varies with
the servo motor and machine operation speeds. (Refer to Fig. 8.3.)
Vo
Lmax t
1
e
60
L max : Maximum coasting distance................................................................................................ [mm][in]
V : Machine rapid feedrate.........................................................................................[mm/min][in/min]
0
J : Servo motor inertial moment .................................................................................[kg•cm
M
J : Load inertia moment converted into equivalent value on servo motor shaft .....[kg•cm
L
τ : Brake time constant (Fig. 8.3)........................................................................................................[s]
t : Delay time of control section (Fig 8.2) ...........................................................................................[s]
e
(There is internal relay delay time of about 30ms.)
(Outside)
Fig 8.1 Temperature Distribution in Enclosure
ON
Emergency
stop(EMG) OFF
Machine speed
Fig 8.2 Dynamic Brake Operation Diagram
J
L
....................................................................................................................... (8.2)
J
M
(Inside)
Air flow
Time constant
V
0
t
e
8 - 3
Time
2 ][oz•in 2 ]
2 ][oz•in 2 ]