VLT
®
5000 Series
■ Mechanical brake control
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 frequency
converter is not able to ‘hold’ the motor, e.g. because
of too high load. In parameter 323 or 326 (relay
outputs 01, 04), select Mechanical brake control
[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 selected and the current is below the level
selected in parameter 223 Warning: Low current,the
mechanical 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
mechanical 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 selected
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.
In extended mechanical brake mode an overcurrent
trip (alarm 13) can be reset by an externally reset.
If the frequency converter is brought into an alarm
condition or an overcurrent or overvoltage situation,
the mechanical brake will immediately cut in.
NB!:
The application shown is only for hoisting
without counterweight.
Control of mechanical brake:
Parameter: Setting: Data value:
323 Relay 01 or par. 326 relay 04 Mechanical brake control [32]
323 Relay 01 or par. 326 relay 04 Extended mechanical brake control [34]
223 Warning: Low current approx. 70% of magnetising current
1)
225 Warning: Low frequency 3-5 Hz
2)
122 Function at stop Pre-magnetisation [3]
120 Start delay time 0.1-0.3 sec.
121 Start function Start frequency/voltage clockwise
3)
[3]
130 Start frequency Set to slip frequency
131 Initial voltage
The voltage must be corresponding to the frequency that has been set in
parameter 130.
1. During start and stop, the current limit in parameter
223 decides the switching level.
2. This value indicates the frequency during ramp-down
at which the mechanical brake is to be closed again.
This assumes that a stop signal has been given.
3. It must be ensured that the motor starts
clockwise (hoist), since otherwise the frequency
converter may drop the load. Switch U, V,
W connections, if required.
MG.51.A9.02 - VLT is a registered Danfoss trademark
88
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