Danfoss VLT Series Programming Manual page 9

Introduction
1 1
4. Control signals from, or internally within, the
frequency converter may in rare cases be
activated in error, be delayed or fail to occur
entirely. When used in situations where safety is
critical, e.g. when controlling the electromagnetic
brake function of a hoist application, these
control signals must not be relied on exclusively.
WARNING
High Voltage
Touching the electrical parts may be fatal - even after the
equipment has been disconnected from mains.
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.
NOTE
Hazardous situations shall be identified by the machine
builder/ integrator who is responsible for taking necessary
preventive means into consideration. Additional
monitoring and protective devices may be included, always
according to valid national safety regulations, e.g. law on
mechanical tools, regulations for the prevention of
accidents.
Protection Mode
Once a hardware limit on motor current or dc-link voltage
is exceeded the frequency converter 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
frequency converter while re-establishing full control of the
motor.
8
®
VLT HVAC Drive Programming Guide
®
MG.11.CC.02 - VLT is a registered Danfoss trademark