ABB ACS800-37-0170-3 - Verifying the capacity of the braking equipment

Resistor braking
222
Verifying the capacity of the braking equipment
1. Calculate the maximum power (P
max
) generated by the motor during braking.
2. Ensure the following condition is met:
The P
brmax
values specified in the technical data table above are for the reference braking cycle
(1 minute of braking, 9 minutes of rest). If the actual duty cycle does not correspond to the reference
cycle, the maximum allowed braking power P
br
must be used instead. In the technical data table,
P
br
is given for two additional braking cycles. See below for directions for calculating P
br
for other
braking cycles.
3. Check the resistors selection. The energy generated by the motor during a 400-
second period must not exceed the heat dissipation capacity E
R
.
If the E
R
value is not sufficient, it is possible to use a four-resistor assembly in which two standard
resistors are connected in parallel, two in series. The E
R
value of the four-resistor assembly is four
times the value specified for the standard resistor.
Custom resistors
Resistors other than the standard resistors can be used provided that:
• the resistance is not lower than with the standard resistors
WARNING! Never use a brake resistor with a resistance below the value specified
for the particular drive / brake chopper / resistor combination. The drive and the
chopper are not able to handle the overcurrent caused by the low resistance.
• the resistance does not restrict the braking capacity needed, i.e.,
where
• the heat dissipation capacity (E
R
) of the resistors is sufficient for the application
(see step 3 above).
P
max
maximum power generated by the motor during braking
U
DC
voltage over the resistor during braking, e.g.,
1.35 · 1.2 · 415 VDC (when supply voltage is 380 to 415 VAC),
1.35 · 1.2 · 500 VDC. (when supply voltage is 440 to 500 VAC) or
1.35 · 1.2 · 690 VDC (when supply voltage is 525 to 690 VAC).
R resistor resistance (ohm)
P
brmax
> P
max
P
max
<
U
DC
R
2