Lenze i550 Series - Page 29

Determine the inverter based on the rated data for the "Light Duty" load characterisc
Check
Output current
Connuous operaon I
out
A I
out
≥ I
N,Mot
/ (k
H,INV
x k
TU,INV
)
Overcurrent operaon cycle 15 s I
out
A I
out
≥ I
N,Mot
x 1.65 / (k
H,INV
x k
TU,INV
)
Overcurrent operaon cycle 180 s I
out
A I
out
≥ I
N,Mot
x 1.25 / (k
H,INV
x k
TU,INV
)
Check motor/inverter combinaon
Calculaon
Motor torque M Nm
( )
æ ö
= - - j ´
ç ÷
ç ÷
j
è ø
2
out,INV
2
N
N,MOT
l
M
M 1 cos
I cos
Check
Overload capacity of the inverter
£
L,max
M
1.5
M
Braking operaon without addional measures
To decelerate small masses, the "DC injecon brake DCB" funcon can be parameterised. DC-
injecon braking enables a quick deceleraon of the drive to standsll without the need for
an external brake resistor.
•
A code can be used to select the braking current.
•
The maximum braking torque to be realised by the DC braking current amounts to approx.
20 ... 30 % of the rated motor torque. It is lower compared to braking acon in generator
mode with external brake resistor.
•
Automac DC-injecon braking (Auto-DCB) improves the starng performance of the
motor when the operaon mode without speed feedback is used.
Braking operaon with external brake resistor
To decelerate greater moments of inera or with a longer operaon in generator mode an
external brake resistor is required. It converts braking energy into heat.
The brake resistor is connected if the DC-bus voltage exceeds the switching threshold. This
prevents the controller from seng pulse inhibit through the "Overvoltage" fault and the
drive from coasng down. The external brake resistor serves to control the braking process at
any me.
The brake chopper integrated in the controller connects the external brake resistor.
Determine brake resistance
Applicaon
With acve load With passive load
Rated power P
rated
kW
³ ´h ´ h ´
1
N max e m
z
t
P P
t
´h ´ h
³ ´
max e m
1
N
z
P
t
P
2 t
Thermal capacity C
th
kWs
³ ´h ´ h ´
th max e m 1
C P t
´h ´ h
³ ´
max e m
th 1
P
C t
2
Rated resistance R
rated
Ω
³
´h ´ h
2
DC
N
max e m
U
R
P
Acve load Can start to move independent of the drive (e.g. unwinder)
Passive load Can stop independent of the drive (e.g. horizontal travelling drives, centrifuges, fans)
U
DC
[V] Switching threshold - brake chopper
P
max
[W] Maximum occurring braking power
η
e
Electrical eciency
η
m
Mechanical eciency
t
1
[s] Braking me
t
z
[s] Cycle me = me between two successive braking processes (t
1
+ dead me)
Informaon on project planning
Project planning process
Dimensioning
29