VLT
®
5000 Series
■ Control of mechanical brake
For hoisting applications, it is necessary to be able
to control an electro-magnetic brake.
For controlling the brake, a relay output (01 or 04) is
required. This output must be kept closed (voltage-
free) during the time when the VLT frequency
converter is not able to ‘hold’ the motor, e.g. be-
cause of too high load. In parameter 323 or 326
(relay outputs 01, 04), select Mechanical brake con-
trol [32] or Extended mechanical brake control [34]
for applications with an electro-magnetic brake.
During start/stop and ramp-down, the output current
is monitored. If Mechanical brake control [32] is se-
lected and the current is below the level selected in
parameter 223 Warning: Low current , the mechani-
cal brake is closed (voltage-free).
As a point of departure, a current can be selected
which is approx. 70% of the magnetising current.
Parameter 225 Warning: Low frequency states the
frequency during ramp-down at which the mechani-
cal brake is to close again.
If Extended mechanical brake control [34] is selected
the mechanical brake is closed (voltage-free) during
start until the output current is above the level se-
lected in parameter 223 Warning: Low Current .
During stop mechanical brake is released until the
frequency is below the level selected in parameter
225 Warning: Low frequency .
Notice by Extended mechanical brake control [34]
that the brake does not close if the output current
gets under parameter 223 Warning: Low current .
Nor does a current low level warning appear.
If the VLT frequency converter is brought into an
alarm condition or an overcurrent or overvoltage situ-
ation, the mechanical brake will immediately cut in.
NB!:
The application shown
is only for hoisting without counterweight.
MG.51.A1.02 - VLT is a registered Danfoss trade mark
94
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