Unidrive Regen Installation Guide
41
Issue Number: 2
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Appendix C
Long cables
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
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
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
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 1
µ
F 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.
Drive
size
Maximum cable length
Cooling requirement
without
additional
ventilation
m
with
additional
cooling
m
1
50
250
One 120mm fan, air flow > 160m
3
/ hr.
2
100
500
One 120mm fan, air flow > 160m
3
/ hr.
3
200
1,000
One 120mm fan, air flow > 160m
3
/ hr.
4
200
1,000
Two 120mm fans, air flow > 160m
3
/ hr., per fan
5
200 per Regen
drive
1,000 per
Regen drive
Two 120mm fans, air flow > 160m
3
/ hr., per fan
NOTE
FS1
FS2
FS3
RFI
SFFL
R
B
Y
3 Phase
Supply
E
E
E
V1
V2
V3
V4
V5
V6
Regen
Inductor
E
E
Switching
Frequency
Filter
RFI
Filter
To
Regen
Drive
Line to
ground
capacitors
