Electric interference limitation
AssigneeVacon Oy
InventorNicklas Södö
Life of this patent
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Abstract
A method and an arrangement for limiting the interference to a common electric power network, generated by a power electronics device, e.g. a frequency converter, which power electronics device comprises of at least one switch type component being able to change the output voltage value at a predefined permissible switching frequency range. The method comprises scanning through the permissible switching frequency range, recording measured common mode current values as a function of the switching frequency, and setting the final switching frequency of the switch type component out of a value where a local maximum value of the common mode current has been recorded.
Claims13
A method of operating a control of a frequency converter,
- the method comprising:
- connecting the frequency converter between a load and a common electric power network without a common mode filter;
- connecting a current measurement circuit for measuring common mode current values between the electric power network and the frequency converter;
- connecting a voltage measurement circuit for measuring the output voltages of the frequency converter;
- scanning, via a control, through a permissible switching frequency range by changing a switching frequency of the at least one switch type component through a whole permissible switching frequency range, the switching frequency being frequency of an average value of the measured output voltages of the frequency converter;
- recording, via the control, the measured common mode current values as a function of the switching frequency;
- setting a switching frequency of at least one switch type component of the frequency converter;
- changing the output value of the at least one switching type component at a predetermined permissible switching frequency range;
- and
- setting, via the control, a final switching frequency of the at least one switch type component to a frequency value where a local minimum value of the common mode current has been recorded.
A control system comprising a control of a frequency converter
- the frequency converter is connected between a load and a common electric power network without a common mode filter,
- a current measurement circuit for measuring common mode current values is connected between the electric power network and the frequency converter,
- a voltage measurement circuit is connected to the output of the frequency converter for measuring the output voltages of the frequency converter,
- wherein the control is configured to:
- scan through a permissible switching frequency range, by changing a switching frequency of the at least one switch type component through a whole permissible switching frequency range, the switching frequency being frequency of an average value of the measured output voltages of the frequency converter,
- record the measured common mode current values as a function of the switching frequency,
- set a switching frequency of at least one switch type component of the frequency converter,
- change the output value of the at least one switching type component at a predetermined permissible switching frequency range,
- and
- set a final switching frequency of the at least one switch type component to a frequency value where a local minimum value of the common mode current has been recorded.
Dependencies are inferred from the claim text.