Dc Braking - Danfoss VLT Brake Resistor MCE 101 Design Manual

Special Conditions Design Guide

7.1.4 DC Braking

Resistor brake is useful from max. speed down to a certain
frequency. Below this frequency DC braking is to be
applied as required. The most efficient way of doing this is
to use a combination of dynamic and DC braking. See
Illustration 7.1. The parameters can be found in
chapter 5 Programming.
7 7
Illustration 7.1 Optimum Braking
How to calculate optimum DC-brake cut in frequency:
n n
−
Slip n
0
s = × 100 %
n
0
f × 60
Synchronous speed [1/min]
n 0 =
p
f = frequency supplied to motor
p = no. of pole pairs
n = speed of the rotor
n
s × f
DC-brake cut in frequency =
2 × Hz
100
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