Smart Logic Control - Danfoss VLT AutomationDrive FC 300 Design Manual

3. Introduction to FC 300
3.8.3. Brake Resistor Cabling
EMC (twisted cables/shielding)
To reduce the electrical noise from the wires between the brake resistor and the frequency converter, the wires must be twisted.
For enhanced EMC performance a metal screen can be used.

3.9.1. Smart Logic Control

3
The Smart Logic Control (SLC) is essentially a sequence of user defined actions (see par. 13-52) executed by the SLC when the associated user defined
event (see par. 13-51) is evaluated as TRUE by the SLC.
Events and actions are each numbered and are linked in pairs called states. This means that when
[1]
is executed. After this, the conditions of
are placed in array parameters.
event
Only one will be evaluated at any time. If an
events
other will be evaluated. This means that when the SLC starts, it evaluates
[1]
is evaluated TRUE, the SLC executes
It is possible to program from 0 to 20
event / action
has been executed, the sequence starts over again from
event [1] / action [1]
events / actions
:
Short Circuit (Motor Phase – Phase)
The frequency converter is protected against short circuits by means of current measurement in each of the three motor phases or in the DC link. A short
circuit between two output phases will cause an overcurrent in the inverter. The inverter will be turned off individually when the short circuit current
exceeds the permitted value (Alarm 16 Trip Lock).
To protect the frequency converter against a short circuit at the load sharing and brake outputs please see the design guidelines.
Switching on the Output
Switching on the output between the motor and the frequency converter is fully permitted. You cannot damage the frequency converter in any way by
switching on the output. However, fault messages may appear.
Motor-generated Overvoltage
The voltage in the intermediate circuit is increased when the motor acts as a generator. This occurs in following cases:
1. The load drives the motor (at constant output frequency from the frequency converter), ie. the load generates energy.
2. During deceleration ("ramp-down") if the moment of inertia is high, the friction is low and the ramp-down time is too short for the energy to be
dissipated as a loss in the frequency converter, the motor and the installation.
3. In-correct slip compensation setting may cause higher DC link voltage.
The control unit may attempt to correct the ramp if possible (par. 2-17
The inverter turns off to protect the transistors and the intermediate circuit capacitors when a certain voltage level is reached.
46
event [2]
will be evaluated and if evaluated TRUE,
event
is evaluated as FALSE, nothing happens (in the SLC) during the present scan interval and no
action [1]
and starts evaluating
events actions
and . When the last
. The illustration shows an example with three
MG.33.BA.02 - VLT
event [1]
action [2]
will be executed and so on. Events and actions
event [1] event [1]
(and only
event [2]
.
Over-voltage Control
.
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FC 300 Design Guide
is fulfilled (attains the value TRUE), action
) each scan interval. Only when
event