Electricity: motive power systems – Induction motor systems – Primary circuit control
Reexamination Certificate
2007-11-13
2007-11-13
Ip, Paul (Department: 2837)
Electricity: motive power systems
Induction motor systems
Primary circuit control
C318S800000, C318S811000, C363S034000, C363S037000
Reexamination Certificate
active
11269805
ABSTRACT:
A method of protecting a frequency converter against overvoltage by controlling an AC motor during braking or during light load and a frequency converter, wherein the frequency converter is a voltage-controlled PWM frequency converter operating in single quadrant (1Q) and comprising at least one uncontrolled rectifier bridge (10) to be connected to a AC supply line (UL1, UL2, UL3), a direct-voltage intermediate circuit and at least one controlled inverter bridge (11) for feeding an AC motor (12) with an alternating voltage (Uu, Uv, Uw) of varying magnitude and frequency, in which method: the angle (θΔ) between the output voltage vector (Us) and current vector (Is), i.e. the power factor, is measured, the angle (θΔ) between the output voltage vector (Us) and current vector (Is), i.e. the power factor, is controlled on the basis of the measurement, and the angle (θΔ) between the output voltage vector (Us) and current vector (Is), i.e. the power factor, is controlled so that the angle does not exceed a preset threshold value, preferably approximately π/2.
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J. Jiang, J. Holtz: J An efficient braking method for controlled AC drives with a diode rectifier front end. Industry Applications Conference, 2000. Conference Record of the 2000 IEEE Oct. 8-12, 2000, Piscataway NJ, USA, pp. 1446-1453. XP010521307. ISBN 0-7803-6401-5.
Ip Paul
Vacon Oyj
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