Danfoss VLT AutomationDrive FC 302 Programming Manual page 9

Introduction Programming Guide
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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 enters the protection
mode. Protection mode means a change of the PWM
modulation strategy and a low switching frequency to
minimise 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 usually 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 zero, which
means that the frequency converter trips immediately if
one of the hardware limits is exceeded.
NOTICE
Disabling Protection mode in hoisting applications
(parameter 14-26 Trip Delay at Inverter Fault=0) is
recommended.
MG33MJ02 Danfoss A/S © Rev. 10/2014 All rights reserved. 7