Emerson Unidrive M201 Installation Manual page 56

4.2.2 Supplies requiring line reactors
Input line reactors reduce the risk of damage to the drive resulting from poor phase balance or
severe disturbances on the supply network.
Where line reactors are to be used, reactance values of approximately 2 % are recommended.
Higher values may be used if necessary, but may result in a loss of drive output (reduced torque at
high speed) because of the voltage drop.
For all drive ratings, 2 % line reactors permit drives to be used with a supply unbalance of up to 3.5 %
negative phase sequence (equivalent to 5 % voltage imbalance between phases).
Severe disturbances may be caused by the following factors, for example:
• Power factor correction equipment connected close to the drive.
• Large DC drives having no or inadequate line reactors connected to the supply.
• Across the line (DOL) started motor(s) connected to the supply such that when any of these
motors are started, the voltage dip exceeds 20 %
Such disturbances may cause excessive peak currents to flow in the input power circuit of the drive.
This may cause nuisance tripping, or in extreme cases, failure of the drive.
Drives of low power rating may also be susceptible to disturbance when connected to supplies with a
high rated capacity.
Frame size 7 has an internal DC reactor and Frame size 8 and 9A have internal AC line reactors so
they do not require AC line reactors except for cases of excessive phase unbalance or extreme
supply conditions. Drive sizes 9E and 10E do not have internal input line reactors hence an external
input line reactor must be used.
When required each drive must have its own reactor(s). Three individual reactors or a single three-
phase reactor should be used.
Reactor current ratings
The current rating of the line reactors should be as follows:
Continuous current rating:
Not less than the continuous input current rating of the drive
Repetitive peak current rating:
Not less than twice the continuous input current rating of the drive
A separate line reactor (INLXXX) of at least the value shown in Table 4-3 and Table 4-4
must be used with size 9E and 10E. Failure to provide sufficient reactance could damage
or reduce the service life of the drive.
CAUTION
56
Unidrive M / HS Frame 7 to 10 Power Installation Guide
Issue Number: 5