Dimensioning Of The Braking Resistor; Installation Of The Braking Resistor - WEG DBW04 Serie Manual Del Usuario

3.3.2 Dimensioning of the Braking Resistor

For the proper dimensioning of the braking resistor, consider the application data, such as:
Desired deceleration time.
„
Load inertia.
„
Braking cycle.
„
In any case, the effective current and maximum braking current values presented in
on page 30 must be observed.
The maximum braking current defines the minimum ohm value allowed for the braking resistor.
The DC link voltage level for actuation of the rheostatic braking is defined by the setting of the
DIP Switch S2 (rheostatic braking actuation voltage), see
The braking resistor power is defined according to the deceleration time, load inertia and
resistive torque.
For most applications, it may be used a resistor with the ohm value indicated in
page 30 and power of 20 % of the rated power value of the driven motor.
Use resistors of STRIP or WIRE type in ceramic support, with proper insulation voltage and that
stand high instant powers in relation to the rated power.
For critical applications with very short braking times, high inertia loads (ex: centrifuges) or
with very short and frequent duty cycles, contact WEG, to define the most suitable resistor.
Note:
The effective braking current presented is just an orientative value, because it depends on the
braking cyclic ratio in the application. In order to obtain the effective braking current, use the
formula below, where t
br
periods during the severest cycle of five minutes.

3.3.3 Installation of the Braking Resistor

Connect the braking resistor between the power terminals +UD and BR, see
page 18.
Separate these power cables from the signal and control wiring. Dimension the cables according
to the application, observing the maximum and effective currents.
If the braking resistor is mounted within the inverter cabinet, take its energy into account when
dimensioning the ventilation of the cabinet.
In order to avoid the destruction of the resistor or risk of fire, include a thermal relay in series
with the resistor and/or a thermostat in contact with its housing, connected in such a way to
disconnect the input power supply of the inverter, as shown in
is given in minutes and corresponds to the sum of the braking actuation
I = I
effective max
Installation and Connection
Table 3.4 on page
√
t
x br
5
Figure 3.5 on page
Table 7.1
22.
Table 7.1 on
Figure 3.5 on
18.
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