Danfoss VLT FC 103 Programming Manual page 8

Introduction
7. Please note that the frequency converter has
more voltage sources than L1, L2 and L3, when
load sharing (linking of DC intermediate circuit)
or external 24 V DC are installed. Check that all
voltage sources have been disconnected and that
the necessary time has elapsed before
commencing repair work.
Warning against unintended start
1. The motor can be brought to a stop by means of
digital commands, bus commands, references or
a local stop, while the frequency converter is
connected to mains. If personal safety consider-
ations (e.g. risk of personal injury caused by
contact with moving machine parts following an
unintentional start) make it necessary to ensure
that no unintended start occurs, these stop
functions are not sufficient. In such cases the
mains supply must be disconnected or the Safe
Stop function must be activated.
2. The motor may start while setting the
parameters. If this means that personal safety
may be compromised (e.g. personal injury caused
by contact with moving machine parts), motor
starting must be prevented, for instance by use
of the Safe Stop function or secure disconnection
of the motor connection.
3. A motor that has been stopped with the mains
supply connected, may start if faults occur in the
electronics of the frequency converter, through
temporary overload or if a fault in the power
supply grid or motor connection is remedied. If
unintended start must be prevented for personal
safety reasons (e.g. risk of injury caused by
contact with moving machine parts), the normal
stop functions of the frequency converter are not
sufficient. In such cases the mains supply must be
disconnected or the Safe Stop function must be
activated.
NOTE
When using the Safe Stop function, always follow the
instructions in the section Safe Stop of the Design Guide.
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.
®
VLT Refrigeration Drive Programming Guide
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.
NOTE
Crane, Lifts and Hoists:
The controlling of external brakes must always have a
redundant system. The frequency converter can in no
circumstances be the primary safety circuit. Comply with
relevant standards, e.g.
Hoists and cranes: IEC 60204-32
Lifts: EN 81
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 s after the last fault and
increases the reliability and the robustness of the
frequency converter while re-establishing full control of the
motor.
In hoist applications "Protection mode" is not usable
because the frequency converter 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
14-26 Trip Delay at Inverter Fault to zero which means that
the frequency converter will trip immediately if one of the
hardware limits is exceeded.
NOTE
It is recommended to disable protection mode in hoisting
applications (14-26 Trip Delay at Inverter Fault = 0)
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MG16H102 - VLT is a registered Danfoss trademark
WARNING
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