Unitronics UMI-B1 UL Series Operation Manual page 22

UMI-B1 UL Series Inverter
Note: Select the fuse as the manual indicated. The fuse will protect the input power
cable from damage in short-circuit situations. It will protect the surrounding devices
when the internal of the inverter is short circuited.
3.3.2 Protecting the motor and motor cables
The inverter protects the motor and motor cable in a short-circuit situation when the
motor cable is dimensioned according to the rated current of the inverter. No additional
protection devices are needed.
•
If the inverter is connected to multiple motors, a separate thermal
overload switch or a circuit breaker must be used for protecting each
cable and motor. These devices may require a separate fuse to cut off
the short-circuit current.
3.3.3 Implementing a bypass connection
It is necessary to set power frequency and variable frequency conversion circuits for the
assurance of continuous normal work of the inverter if faults occur in some significant
situations.
In some special situations, for example, if it is only used in soft start, the inverter can be
conversed into power frequency running after starting and some corresponding bypass
should be added.
•
Never connect the supply power to the inverter output terminals U, V
and W. Power line voltage applied to the output can result in
permanent damage to the inverter.
If frequent shifting is required, employ mechanically connected switches or contactors to
ensure that the motor terminals are not connected to the AC power line and inverter
output terminals simultaneously.
Input cable
Fuse
Figure 3-11 Fuse configuration
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Inverter
Installation guide