Danfoss VLT AutomationDrive FC 300 Design Manual page 12

2. Safety and Conformity
Also make sure that other voltage inputs have been disconnected, such as external 24 V DC, load sharing (linkage of DC intermediate circuit), as well as
the motor connection for kinetic back up.
Systems where frequency converters are installed must, if necessary, be equipped with additional monitoring and protective devices according to the
valid safety regulations, e.g law on mechanical tools, regulations for the prevention of accidents etc. Modifications on the frequency converters by means
of the operating software are allowed.
2
Hoisting applications:
FC functions for controlling mechanical rakes cannot be considered as a primary safety circuit. There must always be a redundancy for controlling external
brakes.
Protection Mode
Once a hardware limit on motor current or dc-link voltage is exceeded the drive will enter "Protection mode". "Protection mode" means a change of the
PWM modulation strategy and a low switching frequency to minimize losses. This continues 10 sec after the last fault and increases the reliability and
the robustness of the drive while re-establishing full control of the motor.
In hoist applications "Protection mode" is not usable because the drive will usually not be able to leave this mode again and therefore it will extend the
time before activating the brake – which is not recommendable.
The "Protection mode" can be disabled by setting parameter 14-26 "Trip Delay at Inverter Fault" to zero which means that the drive will trip immediately
if one of the hardware limits is exceeded.
NB!
It is recommended to disable protection mode in hoisting applications (par. 14-26 = 0)
The DC link capacitors remain charged after power has been disconnected. To avoid electrical shock hazard, disconnect the frequency
converter from mains before carrying out maintenance. When using a PM-motor, make sure it is disconnected. Before doing service
on the frequency converter wait at least the amount of time indicated below:
380 - 500 V
525 - 690 V
12
0.25 - 7.5 kW 4 minutes
11 - 75 kW 15 minutes
90 - 200 kW 20 minutes
250 - 400 kW 40 minutes
37 - 250 kW 20 minutes
315 - 560 kW 30 minutes
MG.33.BA.02 - VLT ® is a registered Danfoss trademark
FC 300 Design Guide