Unidrive M Modular Installation Guide
61
Issue Number: 2
6.3.2 Cooling requirements for higher output
frequencies
Single OTL output sharing chokes - OTLX0X
Up to output frequencies of 300 Hz, 1 m/s airflow provides adequate
cooling.
Above 300 Hz, the following equation must be used to calculate the
required airflow:
S = (f
0.75
/72)
Where:
S
is the airflow in metres per seconds
f
is the drive output frequency in Hz
Example:
Output frequency is 450 Hz
S
= (450
0.75
/72)
= 1.4 m/s
Dual OTL output sharing chokes - OTLX1X
The OTLX1X dual output sharing choke core does not see the change in
drive output frequency as this choke is a current cancelling choke. Only
the drives switching frequency has an effect on the core loss.
Therefore motor frequency is not an issue until higher frequencies cause
high copper losses due to skin effect.
Therefore with the dual OTL chokes, only 1 m/s airflow is required.
Maximum output frequency for OTL chokes
The maximum allowable output frequency for OTL output sharing
chokes, singles or duals, should be limited to 550 Hz.
6.4 Supplying the Unidrive M size 9E/10E
drives with DC / DC bus paralleling
The drive may be supplied with DC instead of 3 phase AC.
The connecting of the DC bus between several drives is typically used
to:
1.
Return energy from a drive which is being overhauled by the
load to a second motoring drive.
2.
Allow the use of one braking resistor to dissipate regenerative
energy from several drives.
There are limitations to the combinations of drives which can be used in
this configuration.
For further information, contact the supplier of the drive for the
Application Note
DC bus paralleling
.
6.4.1 Design data
Capacitance
DC bus capacitance values and peak allowable supply current for
Unidrive M size 9 and 10 drives are as follows.
Table 6-8 DC bus capacitance and peak supply current values
6.5 Control 24 V dc supply
The 24 Vdc supply connected to control terminals 1 & 2 provides the
following functions:
•
It can be used to supplement the drive's own internal 24 V supply
when multiple option modules are being used and the current drawn
by these module is greater than the drive can supply.
•
It can be used as a back-up power supply to keep the control circuits
of the drive powered up when the line power supply is removed. This
allows any fieldbus modules, application modules, encoders or serial
communications to continue to operate.
•
It can be used to commission the drive when the line power supply is
not available, as the display operates correctly. However, the drive
will be in the Under voltage trip state unless either line power supply
or low voltage DC operation is enabled, therefore diagnostics may
not be possible. (Power down save parameters are not saved when
using the 24 V back-up power supply input).
•
If the DC bus voltage is too low to run the main SMPS in the drive,
then the 24 V supply can be used to supply all the low voltage power
requirements of the drive.
Low Under Voltage Threshold Select
(06.067) must also be enabled for this to happen.
Model
Total DC bus
capacitance
µF
Maximum allowable
peak supply current
A
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