Danfoss VT2800 Series Design Manual page 7

circuit are not overloaded, which would dramatically
reduce the service life of the frequency converter.
The frequency converter offers temperature protection
as standard. If there is a thermal overload, this
function cuts out the inverter.
Reliable galvanic isolation
In the frequency converter all digital inputs/outputs,
analogue inputs/outputs and the terminals for serial
communication are supplied from or in connection with
circuits that comply with PELV requirements. PELV is
also complied with in relation to relay terminals, so that
they can be connected to the mains potential.
For further information see the section entitled
Galvanic Isolation (PELV).
Advanced motor protection
The frequency converter has integral electronic
motor protection.
The frequency converter calculates the motor
temperature on the basis of current, frequency and time.
As opposed to traditional, bimetallic protection,
electronic protection takes account of reduced cooling
at low frequencies because of reduced fan speed
(motors with internal fan). This function cannot protect
the indi v idual motors when motors are connected in
parallel. Thermal motor protection can be compared
to a protecti v e motor switch, CTI.
To gi v e the motor maximum protection against
overheating when it is covered or blocked, or if the fan
should fail, you can install a thermistor and connect it
to the frequency converter's thermistor input (Digital
input), see parameter 128 Thermal motor protection.
See also the section entitled Galvanic Isolation
(PELV) for further information.
NB!:
This function cannot protect the indi v idual
motors in the case of motors linked in parallel.
MG.28.E9.02 - VLT is a registered Danfoss trademark
®
VLT 2800 Series
7