Patent Application
20140265971
1. Field of the Invention
The present invention concerns systems using permanent magnet motors as three phase inductors for export power and battery charging for use with electric vehicles, diesel/electric vehicles, and other types of hybrid electric vehicles.
2. Description of Related Art
When a traction motor and an inverter are used for battery charging and export power, the traction motor operates as an inductor, and the inverter performs bi-directional conversion, such that DC/AC conversion is performed for export power, and AC/DC conversion is performed for battery charging. Conventionally, to do this, a grid point is connected to the Y-point on the motor. One problem with typical arrangements is the requirement for three motors and three inverters for a three phase grid connection. In electric vehicle charging applications, large, expensive chargers are typically required, and extra equipment that is both costly and bulky is needed.
One electrical apparatus including a drive system and an electrical machine with a stator winding connectable to a three phase network is disclosed by International PCT Publication WO 2011/159241 A1 to Alaküla et al. Other apparatuses and systems that may be of interest form the subject matter of U.S. Pat. No. 4,920,475 to Rippel, U.S. Pat. No. 5,099,186 to Rippel et al., U.S. Pat. No. 5,341,075 to Cocconi, U.S. Patent Application Publication 2012/0194030 A1 to Brown et al., and Japanese Patent Publication 10-248172 to Tsutomu et al. The disclosures of the Rippel ('475) patent, the Rippel et al. ('186) patent, and the Cocconi ('075) patent are all incorporated herein by reference in their entireties as non-essential subject matter.
One general aspect of this invention concerns applications of a permanent magnet motor as a three phase inductor with motor windings. Other aspects concern use of certain connection architecture, use of a pole count mismatch and an inverter in various application modes, and the possible use of a variety of motor types.
To use a traction motor and inverter as a battery charger or as a DC/AC export power module in a vehicle of the sort referred to above, it is recognized according to the invention that it is possible to use a six pole machine, but switch, with contactors, the stator to a four pole motor, creating a pole-count mismatch between the rotor and stator. One benefit of this feature is that the motor can be used as a three-phase inductor without rotating or producing any torque, and only one inverter is needed. Such an arrangement would also increase inductance as compared to the three motor solution mentioned, since the flux would be linked. Benefits of the present invention could be significant, as an expensive charger could be eliminated, or a diesel electric vehicle could export all its power without any extra equipment, weight, or space beyond what the contactors would require.
An alternative solution would be to break up the neutral point on a permanent magnet motor, and directly connect each winding to each phase on the grid. Due to the high grid frequency (50/60 Hz), the permanent magnet motor will not lock on to the rotating magnetic field, and will therefore produce very low or even zero torque. If a small torque is produced and constitutes a problem for a specific application, a simple on-off brake can be used to eliminate that problem.
According to one preferred embodiment of the invention, a system for providing operating current supply and charging current supply in different modes of operation includes an electric machine including a rotor and a stator having stator windings, at least one charge storage device, such as a battery, or in certain applications, capacitors with a neutral point therebetween that is electrically interconnectable with a neutral wire, and an inverter disposed between the charge storage device terminals and the electric machine. The motor stator includes a plurality of windings, and a contact arrangement is disposed so as to modify electrical interconnections between the inverter and the windings, changing the pole count in the stator. In a supply mode, the electrical interconnections mentioned are controlled using the contact arrangement so that each inverter phase is electrically interconnected with a stator winding set having windings separated from each other by a plurality of stator windings in other winding sets for driving the rotor of the electrical machine. In a charge mode, by contrast, these interconnections are controlled with the contact arrangement so that each inverter phase is electrically interconnected with a stator winding set having windings that are directly adjacent to each other and are not separated from each other. The windings that are directly adjacent to each other, in one arrangement, are connected in parallel in the charge mode. Each inverter phase, in the charge mode, accordingly can receive current supplied from an external source through the stator windings for charging the charge storage device through the inverter.
In certain arrangements, the contact arrangement is disposed between the electric machine and the inverter. The current received by the windings may be supplied from either a polyphase external source, with or without a neutral wire, or a single phase external source. The rotor could be either a permanent magnet rotor, including, for example, six poles, or another rotor appropriate for use in a motor of some other type. In one arrangement suitable for power export, a further inverter can be disposed between the charge storage device terminals and a further electric machine, such as a vehicle battery charging station. A process for providing operating current supply and charging current supply in different modes of operation is also described.
A first connection or lead 38 electrically interconnects with the junction 36, a second connection or lead 40 electrically interconnects with the junction 34, and a third connection or lead 42 electrically interconnects with the junction 32 to enable the inverter 16 to supply current to appropriate windings of an electric machine, which, here, is configured as a motor 44. The motor 44 of this arrangement utilizes a six pole permanent magnet rotor 64 rotatable within a stator 45 supporting nine windings, as indicated in
Each switch of a set of solid state switches (contactors) 46, 48, 50, 52, 54, and 56, as well as each of the grid connection switches 58, 60, and 62, is placed by an appropriate control device (not shown), or by several such control devices, into its proper position in each of the operating modes to be discussed. The switches 46, 48, 50, 52, 54, and 56, collectively, constitute at least part of a contact arrangement disposed so as to modify electrical interconnections between the inverter 16 and the stator windings U1-U3, V1-V3, and W1-W3, as will be described. In the motor mode represented in
By way of the first connection or lead 38, each winding U1, V1, and W1 of the first winding set electrically interconnects with the inverter phase defined by the junction 36. Similarly, by way of the second connection or lead 40, each winding U2, V2, and W2 of the second winding set electrically interconnects with the inverter pole defined by the junction 34, and, by way of the third connection or lead 42, each winding U3, V3, W3 of the third winding set electrically interconnects with the inverter pole defined by the junction 32. The switch elements 20, 22, 24, 26, 28, and 30 of the inverter 16, with its associated capacitor 14, are operated by the control unit to permit appropriate DC flow on the line 18 or 19 and charge the battery 12. Referring now to both
The system 10 is shown in
As illustrated in
The lines 18 and 19 here electrically interconnect the inverter 16 with appropriate terminals of the capacitors 70, 72 as well as to an additional DC/AC inverter 78, including pairs of switch elements, such as the transistors 80 and 86, 82 and 88, and 84 and 90 illustrated. A first connection or lead 92 electrically interconnects a junction 94 forming a pole of the inverter 78 to certain stator windings (not shown) of another electric machine, which, here, is a generator 96. Similarly, a second connection or lead 98 electrically interconnects a junction 100 to respective stator windings of the generator, while a third connection or lead 102 electrically interconnects a junction 104 with further generator stator windings. A mechanical shaft 106 may be used to interconnect the generator 96 and a diesel engine 110.
The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, and the invention should be construed to include everything within the scope of the invention ultimately claimed.
