MGM
80
80
85
90
100
-
-
20
30
30
30
35
-
-
7
9
12
12
14
14
14
BA 71-80-90
BA 100-112
BA 132-160
BA 180-200
BA 225
BA 250
BA 280
33
n = W
tot
/ W
b
BA series
brake linings wear
Brake linings wear is mainly affected by the environmental conditions in which the motor operates, by the frequency of starts, by
the energy dissipated at each stop and by the torque provided by the brake. The lining temperature rises with the braking frequency
and with the moment of inertia applied to the shaft. When the lining temperature raises, the lining wear increases and consequently
the braking time is longer.
BA series motors are designed to have continuous cooling of the braking surfaces so as to reduce
brake disc wear to have a shorter braking time.
The life cycle of the brake linings can be roughly expressed by the number of brake interventions and can be approximately
calculated as follows:
where Wb (J) is the work done during each braking action and Wtot (J) is obtained from the table for each type of brake motor.
However, it is necessary to check the brake disc wear periodically to replace the brake disc before it is completely worn. If you
want to estimate the interval between two successive air gap adjustment in a specific application, note that the brake linings wear
is greater than usual during the run-in (a few thousands stops).
On PV series brake motors Wtot shown in the table have to be multiplied by 0.5 and the moment of inertia have to be calculated
considering the presence of the flywheel. The indicative number of AC brake stops NintAC between two successive air gap
adjustments on a BA motor is given by the following formula:
N
intAC
= E
rBA
/ W
b
while the NintDC for DC brake motors is given by : NintDC = NintAC • 0.65
An indicative braking time t
f
(s) can be calculated as follows:
Motor Type
AC Brake
DC Brake
(Standard)
DC Brake
(Quick)
Starting and braking time
ϕ
s
=
t
a
•
n
19.1
Starting current for an asynchronous motor is always much higher than the nominal current. When the starting time is excessively
long, there are electromechanical disturbances and higher temperatures on winding, damaging the motor. For information on
maximum starting time allowed for each type of motor, please contact MGM. An indicative value for starting time t
s
(expressed
in seconds) and the angle of rotation
ϕ
s
(expressed in radians) can be obtained as follows:
Where J
app
(Kgm
2
) is the moment of inertia referred to the motor shaft, M
load
(Nm) is the opposing torque to the motor, J
mot
(Kgm
2
)
is the moment of inertia of the motor, n (RPM is the rated motor RPM), T is the average starting torque, T=(0,8
÷
0,9)Ts (see the
technical data table for Jmot, n and Ts of the selected motor).
For BA 250-280 pls contact MGM. The indicative number of DC brake stops NintBM between two successive air gap adjustments on a BM
motor is given by the following formula:
N
intBM
= E
rBM
/ W
b
E
rBM
values are shown at pag. 39 (BM section).
Brake electrical reaction time t
B
(ms)
The reported tB times are valid only if the motor is connected with the brake. In case the brake is supplied separately, the tB time has to be cut by
30 – 50%. This calculation gives an approximative indication. Please contact MGM for further information.
Brake Linings Wear, Starting and Braking time
t
s
=
(J
mot
+ J
app
)
•
n
9.55 (T - T
load
)
t
f
=
J
tot •
n
9.55 (T
b
±
T
load
)
+
t
B
1000
J
tot
total moment of inertia at the motor shaft (Kgm
2
)
n
motor RPM (min
-1
)
T
b
brake torque (Nm)
T
load
resisting load torque (Nm) with + sign if matches
the brake torque, or – sign if opposite.
t
B
brake electrical reaction time (ms)
Where:
537
56
705
80
952
95
1148
105
1438
130
2255
200
3290
290
4355
385
4355
385
71
80
90
100
112
132
160
180
200
W
tot
(MJ)
E
r
(MJ)
5226
462
225