Crane System Design; Selection Of Motor Voltage; Selection Of Afe & Lcl Filter; Selection Of Afe For Different Applications - Danfoss VLT AFE 302 Operating Instructions Manual

Crane System Design

3 Crane System Design

3.1 Selection of Motor Voltage

3 3
The AFE system is designed to regulate a DC voltage of
630x1,08x1.41=690V. 690V motors are suitable for this
system.
Furthermore, whenever running the motors in the field
weakening region, or with output LC filters, it is necessary to
use the motors of less than 650V.
3.1.1 Selection of AFE & LCL Filter
•
AFE systems are built up based on standard 690V
hardware.
•
Standard AFE hardware runs on 630V mains supply
and DC-link voltage is 975V.
3.1.2 Selection of AFE for Different
Applications
•
The frequency converter power size in the flux
application must be one or two sizes higher than
the application needed. Also, the frequency
converter should not be higher than two to
maintain a good resolution on current sensors.
•
The size should be selected based on a sum of the
current rather than a sum of the power of the
connected motors.
•
Example:

3.1.3 Selection of Output Filter (LC Filter)

•
The output filter is needed because of the long
motor cable configuration.
•
Output filters should be sized based on the
frequency converter's maximum output current.
•
The dU/dt filters can be used up to 100m to protect
the motor. The sine-wave filters can be used with
any cable length (maximum of 1000m).
8
®
VLT
Hoist motors 500kW @ 650V - Hoist drives
800kW
Travel motors 8x50kW @ 650V - Travel
drive 500kW
Trolley motors 4x55kW @ 650V - Trolley
drive 400kW
AFE/LCL – 1,2MW continuous, with a
175% overload for a maximum 1min.
MG.33.X2.02 - VLT
Active Front End AFE 302 Operating Instructions Liebherr
•
Above 150m cable length it is recommended to
use a sine-wave filter.
•
The cable length is calculated as the sum of all
parallel cables.
•
Filters must be designed to switching frequency of
the frequency converter. The resonance frequency,
f0, of the filter should be:
10 ×
•
The resonant frequency must meet the following
equation, limited by the control frequency, f
f 0 <
Switching frequency [kHz]
1
The control frequency is an internal hardware frequency.

3.1.4 Selection of Switching Frequency

The switching frequency of AFE and motor drives shall be
equal or an integer multiple of each other.

3.1.5 Selection of LCL Filter

The AFE system is designed in conjunction with the
recommended Danfoss LCL filters in which the physical size,
power rating and electrical parameters of the filters are
optimized.
If non-Danfoss filters are used, system performance and
stability may be degraded.

3.1.6 Crane Cable Concept

To reduce the high frequency noise on the mains line and to
meet the EMC emission limits, the electromagnetic coupling
should be avoided and the following rules have to be
applied:
®
is a registered Danfoss trademark
f sw
f out max ≤ f 0 ≤
3
f con
6
Control frequency
1.5
2
2.5
3
3.5
4
5
6
7
:
con
1 [kHz]
3
4
5
6
7
4
5
6
7