Electric vehicle having improved battery reconnect

• US 3,923,116 A
• Filed: 01/02/1974
• Issued: 12/02/1975
• Est. Priority Date: 01/02/1974
• Status: Expired due to Term

• Current Assignee: AEG Westinghouse Transportation Systems, Inc. (Alstom SA)
• Original Assignee: Francis T. Thomspon, James A. Bauer
• Inventors: Bauer, James A., Thomspon, Francis T.
• Primary Examiner(s): Friaglia, Leo
• Assistant Examiner(s): Smith, Milton L.
• Application Number:
  US05/430,107
• Time in Patent Office: 699 Days
• Field of Search: 180/65R,65F,65A,60 318/139,84,95,93,50,81 105/50
• US Class Current: 180/65.8
• CPC Class Codes: B60L 15/04 using dc
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility

Abstract

A method and apparatus for reconnecting batteries of an electric vehicle from parallel to series or from series to parallel with reduced current transients and smooth vehicle operation. When the batteries are to be reconnected to yield a different voltage level they are isolated from the power circuit of the elctric vehicle. Field current flowing through the separately excited field of the direct current drive motor is varied to match the drive motor'"'"''"'"'s operating state for the reconnected voltage level to be provided. When the drive motor is operating at a condition compatible with the new voltage level the batteries are reconnected without excess vehicle jerk or high current transients. The apparatus for isolating the batteries while the field current is being adjusted and for reconnecting the batteries after the field current is adjusted and the motor is brought to a condition compatible with the new voltage may take the form of diodes or a first set of contacts in the parallel paths through the batteries and a contactor or second set of contacts in the series path through the batteries. The contactor or each of the first and second sets of contacts is opened or closed as necessary to isolate or connect the batteries as desired.

Claims

1. A method for switching the poWer batteries connection to the armature of the drive motor in an electric vehicle driven by a separately excited direct current motor from a low voltage connection to a high voltage connection wherein the armature time constant is relatively short and the field time constant is relatively long comprising the steps of:

preventing current flow into the batteries;

increasing the current flowing through the separately excited field windings; and

completing the series connection of the batteries when field excitation reaches a predetermined level of approximately 100% of full field current.

2. A method of switching the series parallel connection of batteries in an electric vehicle propelled by a direct current motor having a separately excited field winding from a first present connection to a second desired connection comprising:

isolating the battery;

changing the field current flowing through the separately excited field to a value compatible with the speed of the direct current motor when operating in the second desired connection; and

connecting the batteries in the second desired connection after the field excitation has had sufficient time to reach the desired value.

3. An electric vehicle insulating switching apparatus for changing the connections of power batteries from parallel to series comprising:

a direct current drive motor for driving the electric vehicle including an armature, having a relatively short time constant, and a motor field winding, having a relatively long time constant, for controlling operation of said direct current drive motor;

a field control means for controlling the current flowing through the motor field winding of said direct current drive motor connected in series with said field winding;

a switch disposed in the series connected electric circuit through the batteries;

at least one of the batteries continuously supplying its output to said armature and said field winding;

said field winding connected in parallel with said armature;

current stopping means disposed in the parallel connected circuit through the batteries to prevent current flow into the batteries during a predetermined period;

sensing means for controlling the field control means to increase current flow through the field windings and for closing said switch at a predetermined field excitation value.

4. Switching apparatus in a moving electric vehicle for changing battery connections from a present connection at a first voltage level to a desired connection at a second voltage level comprising:

a direct current drive motor operable as a motor and as a generator having an armature which has a relatively short time constant;

a separately excited field winding disposed within said direct current drive motor having a relatively long time constant as compared with the armature time constant;

isolating means for preventing current flow into the battery during a switching operation;

switching field control means for changing the current flowing through said separately excited field winding during a switching operation to a value compatible with the second voltage level; and

reconnect means for connecting the batteries in the desired connection and to the drive motor when the field excitation has had sufficient time to reach a satisfactory level.

5. Switching apparatus as claimed in claim 4 wherein said isolating means comprising:

a plurality of diodes;

said diodes being connected in parallel paths through said battery to prevent current flow through parallel battery paths into said batteries; and

including a switch disposed in a series path through said battery and being open during a switching operation to prevent current flow through a series path into said batteries.

6. Switching apparatus as claimed in claim 4 for switching two batteries between series and parallel connections, wherein said isolating means comprises:

a first diode electrically cOnnecting the positive poles of the batteries and being connected to prevent current flow into one of the batteries;

a second diode electrically connecting the negative poles of the batteries and being connected to prevent current flow into the battery;

a switch connecting the positive pole of one battery to the negative pole of the other battery for series operation and being open during a switching operation to prevent series current flowing through the batteries.

7. Switching apparatus as claimed in claim 6 including a diode connected around said switch.

8. Switching apparatus as claimed in claim 4 wherein said isolating means comprises:

a first group of contacts disposed in the parallel paths through said batteries and being open during a switching operation to prevent current flow into the batteries through parallel paths;

a second set of contacts disposed in the series path through said batteries and being opened during a switching operation to prevent current flow into the batteries through the series path.

9. Switching apparatus as claimed in claim 4 for switching two batteries between series and parallel connections, wherein said isolating means comprises:

a first set of contacts electrically connecting the positive poles of the batteries and being open during switching to prevent current flow into one of the batteries;

a second set of contacts electrically connecting the negative poles of the batteries and being open during switching to prevent current flow into the other battery; and

a third set of contacts connecting the positive pole of one battery to the negative pole of the other battery and being open during switching to prevent series current flow through the batteries.

10. An electric vehicle comprising:

a direct current drive motor having an armature which has a short time constant;

a separately excited field winding, having a long time constant, disposed within said direct current drive motor and connected in parallel with said armature;

a plurality of batteries connected to supply power to said direct current drive motor;

switching means for changing the connection of the batteries between a series connection and a parallel connection;

isolating means to prevent current flow into the batteries during connection switching;

switching field control means connected to said separately excited field to vary said separately excited field before a switching operation is completed so as to reduce current transients when said switching means changes the connection of said batteries.

11. An electric vehicle as claimed in claim 10 wherein:

said switching field control means increases the current flow through said separately excited field winding during a switching operation from parallel battery connections to series battery connections; and

said switching field control means decreases the current flow through said separately excited field windings during a switching operation from a series battery connection to a parallel battery connection.

12. An electric vehicle as claimed in claim 10 wherein said isolating means comprises:

a plurality of diodes disposed in the parallel paths through said batteries to prevent current flow into the batteries during switching; and

said switching means comprises a set of contacts disposed in the series path through said batteries.

13. An electric vehicle as claimed in claim 10 wherein:

said isolating means comprises a plurality of contacts, at least one of which is disposed in every current path through said batteries and all of which are open during a switching operation to isolate said batteries from said direct current drive motor.

14. An electric vehicle as claimed in claim 10 wherein said isolating means comprises a switch of said batteries to said direct current drive motor.