DC BUS CLAMP CIRCUIT TO PREVENT OVER VOLTAGE FAILURE OF ADJUSTABLE SPEED DRIVES
First Claim
1. In a power supply having a DC bus providing a DC voltage across a positive and negative bus rail to one or more inverters which provide power to windings of one or more electric motors, the DC bus having at least one capacitive element connected across the positive and negative bus rails, an apparatus for reducing electrical transients on the DC bus comprising:
- at least one damping element having a resistor and a damping capacitor connected in parallel with the resistor; and
a first and a second diode each connected in series with the at least one damping element between the common point and the positive and negative bus rails respectively, such that the direction of conductance of the first diode is from the common point to the positive rail and the direction of conductance of the second diode is from the negative rail to the common point.
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Accused Products
Abstract
The present invention relates to a protective circuit to provide over voltage protection for an ASD. The protective circuit provides the benefits of fewer components with lower power ratings than existing protective circuits. The protective circuit may be incorporated directly in the ASD for continuous protection or mounted externally and connected to the ASD under operating conditions that require the circuit. This flexibility for mounting the protective circuit allows the capacitor of the protective circuit to be sized either in relation to capacitive elements on the DC bus within the ASD or according to external capacitance observed at the output of the ASD. In addition, the circuit is only operative during an overvoltage condition allowing for power ratings lower than would be required for continuous operation.
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Citations
15 Claims
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1. In a power supply having a DC bus providing a DC voltage across a positive and negative bus rail to one or more inverters which provide power to windings of one or more electric motors, the DC bus having at least one capacitive element connected across the positive and negative bus rails, an apparatus for reducing electrical transients on the DC bus comprising:
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at least one damping element having a resistor and a damping capacitor connected in parallel with the resistor; and a first and a second diode each connected in series with the at least one damping element between the common point and the positive and negative bus rails respectively, such that the direction of conductance of the first diode is from the common point to the positive rail and the direction of conductance of the second diode is from the negative rail to the common point. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. The method of reducing electrical transients on a DC bus for an adjustable speed drive, the DC bus having at least one capacitive element, comprising the steps of:
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providing at least one protective circuit including a resistor, a capacitor connected in parallel with the resistor, and a diode connected in series to the parallel connected resistor and capacitor; and connecting the protective circuit in parallel to the capacitive element. - View Dependent Claims (15)
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Specification