Motors-D81.1-complete-English-06-2020

© Siemens 2020
■ Overview
Abbreviations and definitions used
(with their units):
T LR = Motor starting torque (Nm)
T b = Braking torque (Nm)
T breq = Required braking torque (Nm)
T b, rated = Rated torque of the spring-operated brake (Nm)
T L = Load torque (Nm)
T tot = Total torque (Nm)
F =Force (N)
r = Lever arm (m)
n = Speed (rpm)
K = Safety factor K 2
P = Power (kW)
t = Overall braking time (ms)
t st = Startup time (s)
t B = Braking time (s)
t 2 = Disconnection time (ms)
t 1 = Application time (ms)
t 11 = Response delay (ms)
P R = Frictional power (J/s)
W R = Friction energy (J)
S = Switching cycles (brake operations) per second (Hz)
J E = Internal moment of inertia (kgm 2 )
J add = Additional moment of inertia (kgm 2 )
J 2,3.. = Moment of inertia (kgm 2 )
J tot = Total moment of inertia (kgm 2 )
n 1 = Motor speed (rpm)
n 2,3.. =Speeds (rpm)
Multiple moments of inertia with different speeds are converted
into a moment of inertia relative to the motor shaft:
J
J = 2 n 2 2 J 3 n 2 3 (kgm 2 )
add
n 1
2
Torque
A spring-operated brake is designed mainly in accordance with
the required braking torque T breq . If the moment of inertia,
speed, and admissible braking time of the machine are known,
the braking torque of the spring-operated brake can be calculated.
If the masses that are to be decelerated by the spring-operated
brake are running at a different speed from the shaft decelerated
by the spring-operated brake, the moment of inertia of
these masses (J add ) must be calculated relative to this shaft (see
above). In addition, the moment of inertia of the rotor-hub system
(J E ) must be taken into account.
Load torque (static loading)
Torque which is present when the system is at a standstill
and must be held by the brake. The loading force is converted
into the load torque via the relevant lever arm:
T L = F · r (Nm)
Introduction
Mounting technology
Modular technology
Braking torque (dynamic loading)
A purely dynamic load is present when flywheels, rollers, etc.,
are to be delayed and the static load torque is negligibly small.
The required braking torque is calculated as follows:
= 1.046 10 2 n
T b
J tot (Nm)
t
T breq = T b · K T b, rated (Nm)
Dynamic and static loading
Most applications involve dynamic loading as well as static load
torque:
T breq = (T b T L ) K (Nm)
1.046 10 2 n
T breq = ( J tot
T L ) K (Nm)
t t 1
T breq ≤ T b, rated (Nm)
Sign for T L :
+ T L = Load torque is applying force (in the direction of motion)
– T L = Load torque is applying a decelerating force (opposite to
the direction of motion)
If both cases occur, the specific configuration is always adapted
to the larger torque.
Approximate determination of T breq
If the moment of inertia is not known and if the input power has
been defined, the required braking torque is determined as follows:
T breq
K 2
9.55 10 3 P
= K ≤ T b, rated (Nm)
n
Braking time
General information
1.046 10 2 n
t = J tot t (ms) 1
Sign for T L :
T b, rated
t 1
– T L = Load torque is applying force (in the direction of motion)
+ T L = Load torque is applying a decelerating force (opposite to
the direction of motion)
Calculation of the starting and braking time for motors
Startup time for motors with brakes
t st
T L
= n
J 1 t 2
tot
9.55 T L ) 1000
(s)
(T LR
J tot = J E + J add (kgm 2 )
Sign for T L :
+ T L = Load torque is applying force (in the direction of motion)
– T L = Load torque is applying a decelerating force (opposite to
the direction of motion)
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