Accessories; Braking Resistors - KEB COMBIVERT F4-S Serie Manual De Instrucciones

Accessories

3. Accessories
3.1 Braking resistor
Installation Tip
GB
Selection of the braking
resistor
GB - 20
KEB COMBIVERT is equipped with an external braking resistor or an
external braking option and is suited for restricted 4 quadrant operation.
The braking energy that is refed into the intermediate circuit during
regenerative operation is dissipated by means of the braking transistor,
the control and the braking resistor.
The braking resistor heats up during braking. If it is installed inside a
control cabinet sufficient cooling of the control cabinet interior must be
provided and sufficient distance to the KEB COMBIVERT must be kept.
Different braking resistors are available for KEB COMBIVERT. They are
selected according to their application requirements. The respective
formulas and restrictions (validitiy range) are listed on the next page.
1. Preset desired braking time.
2. Calculate braking time without braking resistor (t
3. If the desired braking time is smaller than the calculated braking time,
it will be necessary to use a braking resistor. (t
4. Calculate braking torque (M
5. Calculate peak braking power (P
the "worst case" (n
6. Selection of the braking resistors:
a) P > P
R B
b) P is to be selected in accordance with the cyclic duration factor.
N
The braking resistors may only be used for the units listed. The max.
ON period of the braking resistor may not be exceeded.
Longer ON periods require special-designed braking resistors. Take
into account the continuous output of the braking transistor.
7. Check whether the desired braking time is attained with the braking
resistor (t ).
Bmin
Restriction: Considering the capacity of the braking resistor and the
braking capacity of the motor, the braking torque may not exeed the rated
torque of the motor by more than 1.5 times (see formula).
To utilize the maximum possible braking torque the frequency inverter
must be layed out for the increased current.
) and take the load torque into account.
B
). This must always be calculated for
B
at standstill).
max
).
Bmin
< t
B Bmin)