3.
Verify the selection. See section Calculating the maximum allowed braking power for
a custom duty cycle – ABB chopper and custom resistor (page 230). If necessary, repeat
the pre-selection and verification until you find a suitable drive and chopper combination.
4.
Select a custom brake resistor. See Selecting custom resistors (page 229).
Selecting custom resistors
If you use other than ABB resistor,
1. make sure that the resistance of the custom resistor is greater or equal than the
resistance of the default resistor in the ratings of the custom resistors:
where,
Resistance of the custom resistor
R
Resistance of the default resistor
R
min
WARNING!
Never use a brake resistor with a resistance smaller than R
min
. This will cause
overcurrent that will damage the brake chopper and the drive.
2. the resistance of the custom resistor does not restrict the braking capacity needed, ie.
where,
Maximum power generated by the motor during braking
P
max
Drive intermediate DC circuit voltage
1.35 · 1.25 · 415 V DC (when supply voltage is 380 to 415 V AC)
1.35 · 1.25 · 500 V DC (when supply voltage is 440 to 500 V AC) or
1.35 · 1.25 · 690 V DC (when supply voltage is 525 to 690 V AC)
U
DC
Resistance of the custom resistor
R
3. make sure that the resistor can dissipate the energy transferred to it during the braking:
•
Braking energy is not greater than the resistor heat dissipation capacity (E
r
) during
the period specified. See the custom resistor specification.
• The resistor is installed in a properly ventilated and cooled space. Otherwise the
resistor cannot meet its heat dissipation capacity and overheats.
4. make sure that the instantaneous load capacity of the custom resistor is greater than
the maximum power taken by the the resistor when it is connected to the drive
intermediate DC circuit by the chopper
where,
Instantaneous load capacity of the custom resistor
P
R,inst
Drive intermediate DC circuit voltage
1.35 · 1.25 · 415 V DC (when supply voltage is 380 to 415 V AC)
1.35 · 1.25 · 500 V DC (when supply voltage is 440 to 500 V AC) or
1.35 · 1.25 · 690 V DC (when supply voltage is 525 to 690 V AC)
U
DC
Resistance of the custom resistor
R
Resistor braking 229
To Next Page
Loading...
