Appendix C Long Cables; Exceeding The Maximum Cable Length - Control Techniques Unidrive Regen Installation Manual

Appendix C
C.1

Exceeding the maximum cable length

If the total maximum length specified is exceeded, the increased circulating currents caused by the extra cable capacitance will have an effect on the
other parts of the system. This will necessitate additional components to be added to the standard arrangement.
C.1.1 Regen inductor
If the maximum cable length specified is exceeded this will introduce unnecessary heating of the Regen Inductor. To overcome the additional heating
forced cooling should be introduced into the system as specified in the following table.
The forced cooling should be positioned to provide the specified airflow directly onto the Regen inductor windings.
Table C-1
Maximum cable length
without
Drive
additional
size
ventilation
m
1 50
2 100
3 200
4 200
200 per Regen
5
drive
C.1.2 RFI filter
When an RFI filter is used the capacitors to ground carry common mode current.
When the maximum cable length without additional ventilation specified is exceeded, extra circulating currents can result in heating and saturation of
the RFI filter. To prevent this, some capacitance line to ground should be provided as an additional path for this current, as shown in Figure C-1.
N
NOTE
If the maximum cable length exceeds the maximum cable length with additional cooling, Control Techniques Technical Support must be consulted.
Figure C-1 Unidrive Regen layout
R
FS1
3 Phase
Y
Supply
FS2
B
FS3
C.1.3 Line to ground capacitors for multi-drive systems
Selection of line to ground capacitors for Regen systems with long cables.
In order to select the appropriate capacitors, the rms value of the current line to ground, the AC supply voltage and minimum capacitance values are
required.
A minimum capacitance value of 1µF per phase should be used with the final capacitance value being determined by the value of the current line to
ground. In practice, to carry the required level of current the capacitor will generally have a higher capacitive value. The current rating of the
capacitors should be at a high frequency such as 100kHz at the relevant supply voltage. Polypropylene type capacitors are the most suitable because
of their low loss at high frequency.
Unidrive Regen Installation Guide
Issue Number: 2
Long cables
with
additional
cooling
m
250
One 120mm fan, air flow > 160m
500
One 120mm fan, air flow > 160m
1,000
One 120mm fan, air flow > 160m
1,000
Two 120mm fans, air flow > 160m
1,000 per
Two 120mm fans, air flow > 160m
Regen drive
RFI
V1
V3
V2
V6
V4
V5
E
E
RFI
Filter
www.controltechniques.com
Cooling requirement
3
/ hr.
3
/ hr.
3
/ hr.
3
/ hr., per fan
3
/ hr., per fan
SFFL
E
E
Switching
Line to
Frequency
ground
capacitors
Filter
Regen
Inductor
To
Regen
Drive
E
41