Danfoss VLT FC 102 Programming Manual page 12

®
Introduction
VLT HVAC Drive FC 102
1 1
NOTICE
When using Safe Torque Off, always follow the
®
instructions in VLT Frequency Converters - Safe Torque
Off Operating Instructions.
NOTICE
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, for example when controlling the
electromagnetic brake function of a hoist application, do
not rely on these control signals exclusively.
NOTICE
Hazardous situations must be identified by the machine
builder/integrator who is responsible for considering the
necessary preventive means. More monitoring and
protective devices may be included, always according to
valid national safety regulations, for example law on
mechanical tools and regulations for the prevention of
accidents.
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, for example:
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 enters protection
mode. Protection mode means a change of the PWM
modulation strategy and a low switching frequency to
minimize losses. This continues for 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 is unable to leave this
mode again and therefore it extends the time before
activating the brake, which is not recommended.
Protection mode can be disabled by setting
parameter 14-26 Trip Delay at Inverter Fault to 0, which
means that the frequency converter trips immediately if 1
of the hardware limits is exceeded.
NOTICE
Disabling protection mode in hoisting applications
(parameter 14-26 Trip Delay at Inverter Fault = 0) is
recommended.
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