Layout Protection; Protecting The Vfd And Input Power Cable In Short-Circuit Situations; Protecting The Motor And Motor Cable In Short-Circuit Situations; Protecting The Motor Against Thermal Overload - INVT Goodrive 310-UL Series Operation Manual

GD310-UL series VFD

4.4 Layout protection

4.4.1 Protecting the VFD and input power cable in short-circuit situations

Protect the VFD and input power cable in short circuit situations and against thermal overload.
Arrange the protection according to the following guidelines.
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 VFD
is short circuited.

4.4.2 Protecting the motor and motor cable in short-circuit situations

The VFD protects the motor and motor cable in a short-circuit situation when the motor cable is
dimensioned according to the rated VFD current. No additional protection devices are needed.


4.4.3 Protecting the motor against thermal overload

According to regulations, the motor must be protected against thermal overload and the current must
be switched off when overload is detected. The VFD includes a motor thermal protection function that
protects the motor and closes the output to switch off the current when necessary.

4.4.4 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 VFD if faults occur in some significant situations.
In some special situations, for example, if it is only used in soft start, the VFD can be converted into
power frequency running after starting and some corresponding bypass should be added.

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 VFD output terminals simultaneously.
Input cables
Fuse
Figure 4-26 Fuse configuration
If the VFD 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.
Never connect the supply power to the VFD output terminals U, V and W.
Power line voltage applied to the output can result in permanent damage to
the VFD.
VFD
-31-
Installation guidelines