Lenze DSD - Manual (Page 369)

Lenze · Drive Solution Designer · Manual · DMS 4.2 EN · 12/2013 · TD23
369
12 Components in the DC bus
12.6 Brake resistor selection
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
12.6.2 Interconnection of brake resistors
The resistance value of the brake resistor selected is required to assess in which way the series or
parallel connection has to be selected, so that the total resistance R
sum
is between the minimum
and the maximum resistance value.
• The minimum resistance results from the max. permissible current load of the brake transistor.
• The minimum resistance is part of the technical data of the brake resistor.
• The minimum resistance must not be undershot.
• The maximum resistance results from the max. regenerative power and the switching voltage
U
ch
.
• The maximum resistance must not be exceeded.
• Calculation of the total resistance R
sum
for a group of resistors that are connected in parallel and
in series:
• Calculation of the max. power which the resistor can dissipate:

Note!
• In the case of a series connection the total resistance increases, by which the peak
power that can be maximally dissipated decreases.
• Expanding it with a parallel connection increases the peak power again, but the total
resistance also decreases.
• In any case, the number of connected resistors leads to a proportional increase of
available continuous power and brake energy.
R
sum
Value of the total resistance
R
B
Value of the resistance selected
n
1
Number of the resistors connected in series
n
2
Number of the resistors connected in parallel
R
sum
n
1
R
B
⋅
n
2
----------------- =
P
max
U
ch
2
R
sum
------------ =