Braking Principle And Calculation - Schneider Altivar 61/71 Guía De Explotación

Braking principle and calculation

To obtain a good operating ratio between a drive and a braking unit, the exact motor torque and speed must be known in the various
operating quadrants.
If these two values have an opposing sign, we get the following speed-torque diagram:
1 Motor slowing down to zero speed with constant torque
2 Transient state in a hoisting movement during reversal of up/down direction
3 Slowdown and change of direction for a motor at constant torque
As a general rule, the power is:
Hence, the motor power (+P) is expressed in quadrant I (+T, +n) and III (-T, -n).
The generator power (-P) is expressed in quadrant II (+T, -n) and IV (-T, +n).
In principle, generating loads are divided into two groups:
1 Braking power during deceleration
1
0
t
b
T
T
l
t
b
P
t
b
braki g
40
Generator running
in reverse
- n (REV)
Motor running in
reverse
⋅
C n
----------- -
P =
9,55
n Motor speed
1
T Load torque
l
T Braking torque
b
^
Max. braking power
P
b
t
–
Average braking power during t
P
b
t Braking time
b
t
The braking power is characterized by a peak power
T
b
deceleration, which decreases to 0 in proportion to the speed.
Example: Stopping centrifuges, translational movement, change of direction, etc.
t
P
b
P
b
+ T
Motor running
forward
2
II I
III IV
1
3
Generator running
forward
- T
b
+ n (FWD)
^
P
obtained at the start of
b
1757084 11/2009