Danfoss VLT HVAC Basic Drive FC 100 Series Programming Manual page 12

Introduction
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4. Control signals from, or internally within, the
adjustable frequency drive may in rare cases be
activated in error, be delayed or fail to occur
entirely. When used in situations where safety is
critical, 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 line power.
Also make sure that other voltage inputs have been
disconnected, such as load sharing (linkage of DC
intermediate circuit)
Systems where adjustable frequency drives 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
adjustable frequency drives by means of the operating
software are allowed.
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VLT HVAC Basic Drive Programming Guide
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 adjustable frequency 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
adjustable frequency drive while re-establishing full control
of the motor. Parameter 0-07 Auto DC Braking may cause
PWM when coasted.
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MG18B222 - VLT is a registered Danfoss trademark