Motor controller incorporating an electronic circuit for protection against inrush currents
First Claim
1. An electronic circuit for protection against inrush currents, the circuit comprising:
- an inrush resistor;
a switch, which is controlled by a controller; and
a noise-decoupling capacitor which diverts noise currents to earth;
wherein the circuit is arranged in a DC intermediate circuit and inserted in series with an intermediate capacitor, the inrush resistor having the form of a resistor network connected to the switch, and wherein the controller via the switch alters the resistance of the resistor network, so that when the switch is open, the resistance to a differential current is greater than the resistance to a common mode current, and when the switch is closed, there is greater resistance to a common mode current than to the differential current.
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Accused Products
Abstract
Inrush currents in the dc intermediate circuit of a motor controller necessitate the incorporation of protection circuits. These circuits usually take the form of a resistor inserted in series with the intermediate circuit, and the resistor is short-circuited after completion of inrush by a switch positioned in parallel with the resistor. To reduce cable-transmitted electrical noise an earthed noise-decoupling capacitor is added to the intermediate circuit, but it also requires protection against inrush currents. To minimise the number of components, a protection circuit is described which combines noise filtration and inrush protection. According to the invention, the inrush resistor has the form of a resistor network and is connected to a switch which via a controller alters the resistance of the resistor network, so that when the switch is open, the resistance to a differential current is greater than the resistance to a common mode current, and when the switch is closed, there is greater resistance to a common mode current than to the differential current.
141 Citations
11 Claims
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1. An electronic circuit for protection against inrush currents, the circuit comprising:
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an inrush resistor; a switch, which is controlled by a controller; and a noise-decoupling capacitor which diverts noise currents to earth; wherein the circuit is arranged in a DC intermediate circuit and inserted in series with an intermediate capacitor, the inrush resistor having the form of a resistor network connected to the switch, and wherein the controller via the switch alters the resistance of the resistor network, so that when the switch is open, the resistance to a differential current is greater than the resistance to a common mode current, and when the switch is closed, there is greater resistance to a common mode current than to the differential current. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification