Siemens A1 ユーザーズマニュアル
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Advanced Applications
MICROMASTER Applications Handbook
53
8.5
Vector and FCC Control
8.5.1
What is a Vector Drive?
Vector control is a complex mathematical control function that improves the
performance of an AC drive. It is necessary to understand conventional Voltage to
frequency control and Flux current control in order to understand Vector Control.
performance of an AC drive. It is necessary to understand conventional Voltage to
frequency control and Flux current control in order to understand Vector Control.
Voltage to Frequency Control
A simple inverter drive outputs a variable frequency and voltage to the motor, with
an additional voltage boost (see section 5.8.9) to overcome losses and non
linearity at low frequency. In this case, the voltage rises linearly as the frequency
increases, which theoretically maintains the correct flux level in the motor up to the
base frequency. For pump and fan applications the load is reduced at frequencies
below base frequency, so a reduced voltage is acceptable. In these cases a
quadratic (pump and fan curve) can be specified.
an additional voltage boost (see section 5.8.9) to overcome losses and non
linearity at low frequency. In this case, the voltage rises linearly as the frequency
increases, which theoretically maintains the correct flux level in the motor up to the
base frequency. For pump and fan applications the load is reduced at frequencies
below base frequency, so a reduced voltage is acceptable. In these cases a
quadratic (pump and fan curve) can be specified.
These voltage levels are suitable for many applications. However, for higher
performance a better control strategy is needed. In particular, to offer the same
capability as a DC drive and motor (fast response, torque control, low speed
operation) complex mathematical models of the motor are needed. The
processing power to achieve this has only become available recently at low cost.
Siemens standard drives have offered different solutions such as Flux Current
Control and now offer Sensorless Vector control in some variants.
performance a better control strategy is needed. In particular, to offer the same
capability as a DC drive and motor (fast response, torque control, low speed
operation) complex mathematical models of the motor are needed. The
processing power to achieve this has only become available recently at low cost.
Siemens standard drives have offered different solutions such as Flux Current
Control and now offer Sensorless Vector control in some variants.
8.5.2
What is Flux Current Control?
The Siemens Standard Drives have developed an improved current monitoring
system which allows accurate measurement of the output current with reference to
the motor voltage. This enables the monitoring system to separate the total output
current into the real (load) and imaginary (flux) part.
system which allows accurate measurement of the output current with reference to
the motor voltage. This enables the monitoring system to separate the total output
current into the real (load) and imaginary (flux) part.
I total
I flux
I load
Figure 8-5
Vector Diagram. Load Current against Flux Current
The flux part can then be controlled, and therefore the flux on the motor optimized
for all conditions. This is Flux Current Control (FCC). It has proved very
successful in a wide variety of applications. It offers improved motor efficiency and
better torque and transient response compared to standard Voltage to frequency
operation. It is not as effective as full vector control or sensorless vector control.
for all conditions. This is Flux Current Control (FCC). It has proved very
successful in a wide variety of applications. It offers improved motor efficiency and
better torque and transient response compared to standard Voltage to frequency
operation. It is not as effective as full vector control or sensorless vector control.
Vector Control