BONFIGLIOLI ACTIVE Cube ACU 201-05

18.4.1 Dimensioning of Brake Resistor
WARNUNG
Connect a brake resistor following the instructions and safety information provided in
chapter 6.4.4 “Connection of a Brake Resistor”.
The following values must be known for dimensioning:
− Peak braking power P
b Peak
in W
− Resistance R
b
in Ω
− Operation Time OT in %
• Calculation of peak braking power P
b Peak
( )
b
2
2
2
1
Peak b
t182
nnJ
P
⋅
−⋅
=
P
b Peak
=
Peak braking power in W
J
=
Moment of inertia of drive system kgm
2
n
1
=
Speed of drive system before the braking oper-
ation in min
-1
n
2
=
Speed of drive system after the braking opera-
tion in min
-1
t
b
=
Braking time in s
• Calculation of resistance R
b
Peak b
2
BC d
b
P
U
R =
R
b
=
Resistance in Ω
U
d BC
=
Switch-on threshold in V
P
b Peak
=
Peak braking power in W
The switch-on threshold U
d BC
is the DC link voltage at which the brake resistor is
switched on. The switch-
on threshold can be set, as described above, via parameter
Trigger threshold 506.
CAUTION
The resistance of the brake resistor must not be less than the minimum value R
b min
-
10%. The values for R
b min
are listed in chapter 4 “Technical Data”.
If the calculated resistance R
b
of the brake resistor is between two standard series
values, the lower resistance is to be selected.
• Calculation of operation time OT
cycle
t
b
t
CD =
OT
=
Operation time
t
b
=
Braking time
t
cycle
=
Cycle time
t
cycle
t
b
Example:
t
b
= 48 s, t
cycle
= 120 s
%404.0
cycle
t
b
t
CD ===
In the case of infrequent short braking operations, typical values of the operation
time OT are at 10 %, for long braking operations (≥
120 s) typical values are at
100%. In the case of frequent deceleration and acceleration operations, it is recom-
mended that the operating time OT be calculated according to the above formula.
The calculated values for P
b Peak
, R
b
and OT can be used by the resistor manufactur-
ers for determining the resistor-specific permanent power.
244 Operating Instructions ACU 06/13