The way to the suitable brake
Brakes have been in KEB's DNA since the company was founded. Building on decades of expertise, we have summarised the most relevant units for you on this page, which should be taken into account during dimensioning.
Dimensioning and calculations of brakes
Decisive for the dimensioning of the clutches and brakes are the required torque, thermal load, braking time and service life.
Rated torque M2
To ensure that brakes and clutches work safely even under extreme conditions, the required torque must be multiplied by a safety factor. The selection of the safety factor K depends essentially on the application.
The dynamic torque of a single-disc brake may be substantially lower than the rated torque 4).
Merf = required torque (Nm)
K = safety factor
REQUIRED TORQUE Merf
The required torque very often is a mixture of dynamic and static load. When choosing the sign take into account whether the load torque supports or counteracts the deceleration.
MA = dynamic braking torque (Nm)
ML = load torque (Nm)
J = moment of inertia (kgm²) 1)
α = angular acceleration (s⁻²)
Rough definition of the required braking torque
If the mass moment of inertia is unknown and the driving power is fixed then the required braking torque is calculated as follows:
P = engine power (kW)
n = speed (1/min)
Thermal load
The dimensioning solely on the basis of the required braking torque is permissible only in very few cases. When decelerating the load and the mass moment of inertia is reduced to the brake shaft, the kinetic energy is converted into heat (friction work of the brake). The permissible friction work in dependence on the switching frequency may not be exceeded.
Please note that the maximal permissible friction work is valid only up to the corresponding speed. In case of emergency stop from maximum speed the maximal permissible friction work lies considerably below the values specified in the graphic.
WR = friction (J)
J = moment of inertia (kgm²) 1)
n = speed (1/min)
M2 = static rated torque (Nm) 4)
ML = load torque (Nm) 3)
SLIP TIME t3 [ms]
The time from the beginning of the torque rise until attaining the moment of synchronization.
J = moment of inertia (kgm²) 1)
n = speed (1/min)
M2 = static rated torque (Nm) 4)
ML = load torque (Nm) 3)
Service life
The service life 2) depends to a large extent on the peak temperature at braking, which is dependent on the speed, the deceleration time and the current
brake torque.
For that reason it is not possible to make universally valid statements with regard to the service life that apply to all operating conditions. Statements to
the individual case can be made only when all operating conditions are known. At no time should the friction lining thickness (COMBISTOP) be less than gmin.
X = rated air gap (mm)
Xn = clearance at which an adjustment is recommended (mm)
WR = friction (J)
WR0,1 = fricion work up to 0,1 mm wear (J)
J = moment of inertia (kgm²) 1)
n = speed (1/min)
Acceleration- / Deceleration time
J = moment of inertia (kgm2) 1)
ω = angular frequency (s-1)
M2 = static rated torque (Nm) 4)
ML = load torque (Nm) 3)
t1 = switch on time
Deviations COMBIBOX
1) Sum of the moment of inertia reduced to the speed of the COMBIBOX plus the moment of inertia of the COMBIBOX parts to be accelerated or decelerated.
2) Number of switchings until readjustment. For type 06 and 10 the friction TR of the clutch as well as the friction TR of the brake are to be considered.
3) For the selection of the sign take notice of whether the load torque supports or counteracts the acceleration or deceleration.
4) The rated torques listed in the tables are safely attained after a run-in phase at 100 rpm. In new condition and for substantially higher speeds the
torques are possibly lower.
