Sizing The Braking Resistor - WEG CFW-11 User Manual

3.2.3.2.1 Sizing the Braking Resistor

The following application data shall be considered for the adequate sizing of the braking resistor:
- Desired deceleration time;
- Load inertia;
- Braking duty cycle.
In any case, the effective current value and the maximum braking current value presented in table 3.4 shall
be respected.
The maximum braking current defines the minimum braking resistor value in ohms.
The DC bus voltage level for the activation of the dynamic braking function is defined by parameter P0153
(dynamic braking level).
The power of the braking resistor is a function of the deceleration time, the load inertia, and the load torque.
For most applications, a braking resistor with the value in ohms indicated in table 3.4 and the power of 20 %
of the rated driven motor power. Use wire type resistors in a ceramic support with adequate insulation voltage
and capable of withstanding high instantaneous power with respect to rated power. For critical applications with
very short deceleration times and high inertia loads (ex.: centrifuges) or short duration cycles, consult WEG for
the adequate sizing of the braking resistor.
Inverter model
CFW11 0142 T 2 O DB
CFW11 0180 T 2 O DB
CFW11 0211 T 4 O DB
CFW11 0105 T 4 O DB
CFW11 0142 T 4 O DB
CFW11 0180 T 4 O DB
CFW11 0211 T 4 O DB
(1) The effective braking current presented is just an indicative value, because it depends on the braking duty cycle. The effective braking current
can be obtained from the equation below, where t
cycle of 5 (five) minutes.
t
br
I = I x
effective max
5
(2) The P and P values (maximum and mean power of the braking resistor respectively) presented are valid for the recommended resistors and
max R
for the effective braking currents presented in table 3.4. The resistor power shall be changed according to the braking duty cycle.
(3) For specifications on the recommended terminal type (bolt and tightening torque) for the connection of the braking resistor (terminals DC+
and BR), refer to the DC+ terminal specification at the table 3.2.
Table 3.4 - Dynamic braking specifications
Maximum Maximum
braking braking power
current (peak value)
(I ) (P )
(2)
max max
[A] [kW]
266.7 106.7
266.7 106.7
333.3 133.3
186.0 148.8
266.7 213.3
266.7 213.3
363.6 290.9
is given in minutes and corresponds to the sum of all braking times during the most severe
br
Installation and Connection
Dissipated
Effective
power (mean
braking
value) in
current
the braking
(I )
(1)
resistor (P ) (2)
effective
[A]
R
[kW]
142.0 30.2
180.0 48.6
211.0 53.4
105.0 47.4
142.0 60.5
180.0 97.2
191.7 80.8
Power wire
Recommended size (terminals
resistor DC+ and
[Ω] BR)
(3)
[mm 2 (AWG)]
70 (2/0) or
1.5
2x 25 (2x 4)
120 (4/0) or
1.5
2x 35 (2x 2)
150 (300) or
1.2
2x 50 (2x 1)
4.3 50 (1)
70 (2/0) or
3.0
2x 25 (2x 4)
120 (4/0) or
3.0
2x 35 (2x 2)
120 (250) or
2.2
2x 50 (2x 1)
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