Lenze m850 Series Project Planning page 52

Product extensions
Brakes
To simplify matters, the friction energy per switching cycle can be calculated using the formula
below and must not exceed the limit value for emergency stops, which depends on the
switching rate:
æ D
1 n
= ´ ´ p ´
Q J 2
ç
ges
2 60
è
The shortest operating times of the brakes are achieved by DC switching of the
voltage and an external suppressor circuit (varistor or spark suppressor).
Without suppressor circuit, the operating times may increase. A varistor/ spark
suppressor limits the breaking voltage peaks. It must be ensured that the power
limit of the suppressor circuit is not exceeded. This limit depends on the brake
current, brake voltage, disengagement time and the switching operations per
time unit.
Furthermore the suppressor circuit is necessary for interference suppression
and for increasing the service life of the relay contacts (external, is not
integrated into the motor).
It is not possible to readjust the brake.
52
Q
J
2
ö
M
total
N
´
÷
- Δn
M M
ø
N L
M
N
M
L
J Friction energy
Total mass inertia (motor + load)
2
kgm
rpm Differential speed
Nm Rated torque of the brake
nM Load torque