Operating Instructions ACU
13 Operating behavior
The operational behavior of the frequency inverter can be adjusted to the application by setting the
parameters appropriately. In particular the acceleration and deceleration behavior can be selected
according to the selected Configuration 30. Additionally, features such as Auto Start, and the
synchronization and positioning functions facilitate the integration in the application.
13.1 Starting behavior
The start of the 3-phase machine can be parameterized in accordance with the control functions and
methods. In contrast to the sensorless control method, the field-oriented control methods only
require the definition of the limit values Max. Flux-Formation Time 780 and Current during Flux-
Formation 781 for the adjustment of the acceleration behavior. The acceleration behavior of the
sensorless control method in configurations 110 and 111 can be selected as described in the
following chapter.
13.1.1 Starting Behavior of Sensorless Control System
Parameter Operation Mode 620 for the starting behavior is available in Configurations 110 and 111.
Depending on the operation mode selected, the machine is magnetized first or a starting current is
impressed. The voltage drop across the stator resistance which reduces the torque in the lower
frequency range can be compensated by the IxR compensation.
To ensure the correct function of the IxR compensation, the stator resistance is determined during
the guided commissioning. The IxR compensation is only activated when the stator resistance was
determined correctly.
During startup, at an output frequency of 0 Hz, the voltage is set via
parameter Starting Voltage 600. After this, the output voltage and the
output frequency are changed according to the control method.
The break-away torque and the current at the start is determined by the
adjusted starting voltage. It may be necessary to optimize the starting
behavior via the parameter Starting Voltage 600.
In this operation mode, the Current during Flux-Formation 781 for
magnetization is impressed into the motor after release. The output
frequency is kept at 0 Hz for the Max. Flux-Formation Time 780. After
this time has expired, the output frequency follows the adjusted V/f
characteristic. (see operation mode 0- Off)
Magnetisation+Cur
rent Impr.
Operation mode 2 includes operation mode 1. Once the Max. Flux-
Formation Time780 has elapsed, the output frequency is increased
according to the set acceleration. If the output frequency reaches the
value set with the parameter Frequency Limit 624 the Starting Current
623 is withdrawn. There is a smooth transition to 1.4 times the
frequency limit to the set V/f characteristic. As from this operating point,
the output current depends on the load.
Magnetization
+ IxR
compensation
Operation mode 3 includes operation mode 1 of the start function. When
the output frequency reaches the value set with parameter Frequency
Limit 624, the increase of the output voltage by the IxR compensation
becomes effective. The V/f characteristic is displaced by the portion of
voltage which depends on the stator resistance.
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