892 HEIDENHAIN Technical Manual MANUALplus 620
Limitation of the 
braking power
The use of energy recovery and/or a braking resistor must also be taken into 
account when braking the drives in an emergency stop or in the event of a 
power failure:
Inverter without energy recovery (with braking resistor):
 MP_motPbrMax: Calculate the maximum braking power from the formula 
below.
 MP_motPbrMaxAcFail: Calculate the maximum braking power from the 
formula below.
Inverter with energy recovery (without braking resistor):
 Enter MP_motPbrMax = 0 so as not to limit the braking power.
 MP_motPbrMaxAcFail: The braking power cannot be limited in a power 
failure. Axes and spindles will coast to a stop.
Inverter with energy recovery and additional braking resistor:
 Enter MP_motPbrMax = 0 so as not to limit the braking power.
 MP_motPbrMaxAcFail: Calculate the maximum braking power from the 
formula below.
Calculation of maximum braking power:
 For inverters with braking resistor, calculate the maximum braking power 
from the following formula:
R = Braking resistance [Ω] 
U
Z
 = DC-link voltage [V] 
Max. braking power
U
Z
2
R 1000⋅
--------------------------=
 If the braking power defined in MP_motPbrMax or 
MP_motPbrMaxAcFail is smaller than the one defined in 
MP_maxAcceleration, the braking power from MP_maxAcceleration is 
used for braking.
 If after entry of a value in MP_motPbrMax or MP_motPbrMaxAcFail, 
the mechanics are overloaded by the braking process, reduce the value 
until you have found an optimum between braking time and mechanical 
load.