Single current regulator for controlled motoring and braking of a DC-fed electric motor
First Claim
1. Control apparatus for a DC-fed motor control system, comprising:
- an electric machine having an armature winding;
a rechargeable source of DC normally connected to a DC bus;
DC bus switching means connecting the armature winding to the DC bus, including transistor means for supplying current to the armature winding from the DC bus, and rectifier means for returning current from the armature winding to the DC bus;
current control means for modulating the transistor means (1) during a motoring mode of operation to control the current supplied to the armature winding, and (2) during a braking mode of operation to control the current returned to the DC bus;
an energy exchange capacitor connected across the DC bus;
a load resistor;
mode switching means effective when activated to interrupt the connection of the source to the DC bus, and to connect the load resistor across the DC bus in parallel with the capacitor;
sensing means effective during the braking mode of operation for detecting an operating condition for which the modulation of the transistor means is ineffective to control the current returned to the DC bus; and
means for activating the mode switching means in response to the detection of said operating condition by the sensing means, whereafter the capacitor takes the place of the source, the current returned to the DC bus is supplied to the load resistor, and the modulation of said transistor means become effective to control such returned current.
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Accused Products
Abstract
A control system for an electric machine powered from a DC source, wherein controlled motoring and controlled braking are achieved with a single current regulator control, even when the DC source cannot accept charging current and/or the induced motor voltage exceeds the DC bus voltage. The motor control circuit comprises a DC source connected to a DC bus, a current control circuit for modulating switching devices connected across the DC bus, an energy exchange capacitor connected across the DC bus, a load resistor, a switching circuit effective when activated to interrupt a connection between the DC source and the DC bus and to connect the load resistor across the DC bus in parallel with the capacitor, and a logic circuit for activating the switching circuit during motor braking under conditions for which the modulation of the switching devices is ineffective to control the braking current.
103 Citations
10 Claims
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1. Control apparatus for a DC-fed motor control system, comprising:
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an electric machine having an armature winding; a rechargeable source of DC normally connected to a DC bus; DC bus switching means connecting the armature winding to the DC bus, including transistor means for supplying current to the armature winding from the DC bus, and rectifier means for returning current from the armature winding to the DC bus; current control means for modulating the transistor means (1) during a motoring mode of operation to control the current supplied to the armature winding, and (2) during a braking mode of operation to control the current returned to the DC bus; an energy exchange capacitor connected across the DC bus; a load resistor; mode switching means effective when activated to interrupt the connection of the source to the DC bus, and to connect the load resistor across the DC bus in parallel with the capacitor; sensing means effective during the braking mode of operation for detecting an operating condition for which the modulation of the transistor means is ineffective to control the current returned to the DC bus; and means for activating the mode switching means in response to the detection of said operating condition by the sensing means, whereafter the capacitor takes the place of the source, the current returned to the DC bus is supplied to the load resistor, and the modulation of said transistor means become effective to control such returned current. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification