Frequency limits, Voltage loop, Frequency limits -15 voltage loop -15 – Rockwell Automation 20L, LPM20 PowerFlex 700 Active Converter Power Module User Manual
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2-15
PowerFlex 700L Active Converter Power Module User Manual
Frequency Limits
The PWM Carrier Frequency is fixed at 4 kHz and cannot be changed.
If operating on a generator, the normal range of acceptable AC line
frequencies may need to be expanded. The limit of the rate of change may
also need to be adjusted to allow the line synchronization to properly track
the changes in frequency. See Converter parameters 131 - [AC Low Freq
Lmt] through 135 - [AC Maximum dF/dt].
Voltage Loop
The voltage major loop uses Vdc Reference and Vdc Feedback to calculate
the required active current to maintain a constant DC bus voltage.
Voltage Reference Selection
Converter parameter 160 - [Voltage Loop Sel] selects the value used for the
DC Link voltage reference. One of two values may be chosen at this time;
“0 = Optimized Ref” and “1 = Manual Ref.” The Regen Only option is
reserved for future enhancements, and the Open Loop option is reserved for
manufacturing tests. A password must be entered to use the Open Loop
option.
When “0 = Optimize Ref” is selected, the value for the DC Link reference is
calculated as the minimum value for the given operating condition to reduce
switching losses and increase efficiency. The base value for DC Link
reference is 1.44 times the RMS AC line. For a 480 volt line, the DC link
reference starts at 692 Vdc. This is 2% above the peak of the AC line. In
applications where the maximum motor voltage is greater than the AC line,
the Converter can boost the DC link to a higher level. The Inverter
calculates the minimum required DC link for the present motor voltage and
transmits that value to Converter parameter 72 - [Converter Min Vdc]. As
the line voltage goes up and down and as the Inverter’s motor voltage goes
up and down, the DC Link reference goes up and down to match the
operating conditions.
This option is most useful when there are significant changes in the line
voltage. This option is not recommended for common bus applications
where multiple Inverters operate at different speeds.
When “1 = Manual Ref” is selected, the value for DC Link reference is the
value in parameter 60 - [DcLink Reference]. If the peak of the AC line
becomes greater than the entered value, then the AC line will over-ride to
keep the DC link reference at least 1.44 times the RMS AC line. This option
is intended for operating at a specific DC Link voltage, or in situations were
the Converter is regulating a common bus for multiple Inverters and an
external controlling device is calculating the required DC Link voltage.
The currently commanded DC Link voltage is displayed in parameter 161 -
[DcLink Command].