Dynamic Brake Characteristics; Dynamic Brake Operation - Mitsubishi Electric Melservo MR-J3-A Instruction Manual

11. CHARACTERISTICS

11.3 Dynamic brake characteristics

11.3.1 Dynamic brake operation

Fig. 11.3 shows the pattern in which the servo motor comes to a stop when the dynamic brake is operated.
Use Equation 11.2 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 (2) (a), (b) of this section.)
Emergency stop(EMG)
J
V
0
L t
1
e
max
60
J
L : Maximum coasting distance .................................................................................................... [mm][in]
max
Vo : Machine rapid feed rate ..............................................................................................[mm/min][in/min]
J : Servo motor inertial moment..................................................................................... [kg cm
M
J : Load inertia moment converted into equivalent value on servo motor shaft ............ [kg cm
L
: Brake time constant .......................................................................................................................... [s]
t : Delay time of control section............................................................................................................. [s]
e
For 7kW or less servo, there is internal relay delay time of about 30ms. For 11kW to 22kW servo,
there is delay time of about 100ms caused by a delay of the external relay and a delay of the
magnetic contactor built in the external dynamic brake.
(2) Dynamic brake time constant
The following shows necessary dynamic brake time constant for the equations (11.2):
(a) 200V class servo motor
25
20
15
73
10
5
0
0 1000 2000
HF-MP series
ON
OFF
V
Machine speed
Fig. 11.3 Dynamic brake operation diagram
L
....................................................................................................................... (11.2)
M
23
43
053
13
3000 4000 5000 6000
Speed [r/min]
0
t
e
25
20
15
10
11 - 6
Time constant
Time
73
053
13
5
43
0
0 1000 2000 3000 4000 5000 6000
Speed [r/min]
HF-KP series
2 2
][oz in ]
2 2
][oz in ]
23