Harmonic Distortion; Regenerative Power - ABB ACS850 Application Manual

I
•
mot
I
•
mot
Where:
• I
mot,ave(i)
•
P
rec,ave(i)
concerned AC input
• P
rec,ave1
connected to the AC input
the factor 1.20 covers the load unbalance due to the variation of the characteristics
•
of the individual choke(s) and drive module(s) from the nominal ones
• I
mot,ave
case.

Harmonic distortion

If there are requirements for harmonic distortion level, a mains choke (CHK-xx) is
typically needed in ACS850 frames A and B. Other drive types have a choke as
standard.
Total harmonic distortion is about 40...45%, when a choke is used according to default
selection. Then also the requirements for harmonic distortion according to standards
IEC 61000-3-2, IEC 610003-4, and IEC 610003-12 are typically fulfilled.
A more accurate harmonics analysis can be made with the sizing tool DriveSize. See
also ABB's Guide to Harmonics with AC Drives in AC Drives Technical Guide Book for
basic theory about this topic.

Regenerative power

Regenerative power is fed by the motor to the DC link when the motor produces
negative torque and then brakes. This is typical when the motor is decelerating or
when the motor is in a so called generator mode (for example, unwinder). If the other
drive modules do not take enough active power from the DC link at the same time, the
braking energy is stored in the DC link capacitors and the DC link voltage increases. A
low amount of regenerative energy can be handled within the common DC capacitors if
the DC link voltage stays below the trip limit.
The regenerative energy should be removed from the system if the energy capacity of
the common DC system is not enough. This can be done by braking resistors or by
feeding the excess energy back to the supply network. Either resistor braking or an
external regenerative supply unit can be used.
= ×
1 20
.
, ave ( ) i
( P
rec , ave
= ×
1 20
.
,max( ) i
( P
rec ,max
and I are the AC input currents of the concerned AC input
mot,max(i)
and P are the power ratings of the drive module connected to the
rec,max(i)
... P and P
rec,aven rec,max1
and I are calculated from P
mot,max
P
rec , ave ( ) i
+ + +
P ... P
1 2
rec , ave rec , aven
P
rec ,max( ) i
+ + +
P ... P
1 2
rec ,max rec
... P are the power ratings of the drive modules
rec,maxn
and P
mot,ave
×
I
mot , ave
)
×
I
mot ,max
)
,max n
as in the single AC input
mot,max
Common DC configurations
27