ABB ACS880-04 drive modules - DC Contactors; DC Link Separation; Brake Resistor Protection

34 Planning – additional instructions
DC contactors
 DC link separation
If you connect drives with different type of charging circuits to the AC power line, you must
separate their DC link with a DC contactor. The DC links of drives with Ty pe B charging
circuit may not be connected to the DC link of drives with Type A charging circuit during
the charging. See the table in section Power correction factor (k) on page 41.
The contactor must be open during the power up until the separate DC links are charged
and the drives are in Ready state. Then you can close the contactor and connect the DC
links.
Select the DC contactor in the DC link using these values:
U
dc_max
= 1.21 × 1.35 × U
1
I
dcN
= P
DC
/ U
dc
P
DC
≈ P
cont.max
 Brake resistor protection
If you use resistor braking, you must make sure that if the chopper fails and it cannot
switch off, the system will cut off the power supply for the brake resistor.
• If you use the chopper in a drive with Type B charging circuit, and that drive is the only
one that you connect to the AC power line, you do not need extra protection: The drive
detects the chopper fault, and its input bridge cuts off the power supply from the AC
power line to DC link and further to the resistor.
• If you use the chopper in a drive with Type A charging circuit, or connect several drives
to the AC power line, install a DC contactor between the chopper and brake resistor,
and wire the chopper fault relay to open the contactor control circuit after the chopper
fault.
Select the DC contactor for the chopper using these values:
U
dc
= 1.35 × U
1
I
p
= (1.25 x U
dc
) / R
brake
I
rms
= (P
br
/ R
brake
)
½
I
dcN
Nominal DC current in the DC link
P
cont.max
Power rating of the larger drive to be separated (See the drive hardware manual.)
U
1
AC input voltage of the drive
U
dc_max
Maximum voltage over the contactor in the DC link
I
p
Peak current during the resistor braking
I
rms
Nominal rms current during the resistor braking
P
br
Motor braking power that the resistor must dissipate
R
brake
Resistance of the brake resistor
U
1
AC input voltage of the drive
U
dc
Voltage over the contactor during the braking