Cost effective measurement of high currents

• US 6,528,960 B1
• Filed: 11/08/2000
• Issued: 03/04/2003
• Est. Priority Date: 11/08/2000
• Status: Expired due to Term

• Current Assignee: BAE Systems Controls Incorporated (BAE Systems Plc)
• Original Assignee: BAE Systems Controls Incorporated (BAE Systems Plc)
• Inventors: Basselgia, Mark William, Roden, Garey George
• Primary Examiner(s): Dang, Khanh
• Application Number:
  US09/708,111
• Time in Patent Office: 846 Days
• Field of Search: 318/138, 318/254, 318/268, 318/801, 318/806, 318/811, 324/126, 361/31, 361/58
• US Class Current: 318/400.32
• CPC Class Codes: G01R 1/203 Resistors used for electric measuring, e.g. decade resistors standards, resistors for comparators, series resistors, shunts resistors in general H01C; microwave or radiowave terminations H01P1/26; coupling devices H01R
• CPC Class Codes: G01R 15/18 using inductive devices, e.g. transformers
• CPC Class Codes: G01R 19/0092 measuring current only all subgroups of G01R19/00 take precedence

Abstract

The increasing use of vehicles powered completely or in part by electric motors has created a need for measuring high currents in an inexpensive, reliable and convenient manner for digital motor control. Because the operating voltages of traction motors may be high, it is desirable that the motor current sensors be noncontacting. High-current sensors are commercially available, but tend to be large and costly. According to an aspect of the invention, a noncontacting current sensor having a rated capacity significantly less than the motor (or other) current to be measured is coupled to an electrical conductor for sensing the current in that conductor. The electrical conductor is paralleled by one or more additional similar conductors, so that only a fraction or portion of the current to be measured flows through the conductor associated with the sensor. The current sensor elements may be mounted on a printed-circuit board, which supports the elements, and also has one or more printed patterns which define a conductor associated with the sensor and at least one other conductor through which current can flow in parallel with the current in the sensor.

Claims

1. A device for determining electrical current, said device comprising;

a current sensing apparatus, said current sensing apparatus including a first electrical path through which a current to be sensed passes, said current sensing apparatus being capable of producing a sensed signal in linear response to the current in said first electrical path, up to a predetermined maximum value of said current in said first electrical path, above which current said sensed signal is limited;

first and second terminals coupled to ends of said first electrical path, whereby said current sensing apparatus produces said sensed signal in response to current flowing between said first and second terminals up to said predetermined maximum value; and

a second electrical path extending between said first and second terminals, said second electrical path being effectively in parallel with said first electrical path, so that a portion of current flowing between said first and second terminals flows through said second electrical path rather than through said first electrical path, whereby the non-limited portion of said sensed signal represents a current between said first and second terminals which is less than said current above which said sensed signal is limited, and whereby said device may be used to provide a signal indicative of the magnitude of said current flowing between said first and second terminals.

2. A device according to claim 1, wherein said current sensing apparatus is noncontacting as between said first current sensing path and that port at which said sensed signal is generated.

3. A vehicle powered at least in part by an electric motor, said vehicle comprising:

a rotational vehicle drive device;

a motor coupled to said rotational vehicle drive device, for driving said vehicle when said motor drives said rotational vehicle drive device;

a source of electrical energy;

an electrical power path extending between said source of electrical energy and said motor, said electrical power path including a controllable electrical power control arrangement, for controllably coupling electrical energy between said source of electrical energy and said motor;

a control circuit coupled to said controllable electrical power control arrangement, for responding to at least operator control signals and motor current signals, for controlling said motor for driving said vehicle under operator control;

a current sensing apparatus located in said electrical power path, for sensing at least one component of motor current, said current sensing apparatus having a maximum motor current component below which a nonlimited sensed signal linearly representative of said motor current component is generated and above which said sensed signal is limited; and

a resistive shunt paralleling said current sensing apparatus, for shunting at least a portion of said motor current component around said current sensing apparatus.

4. A vehicle according to claim 3, wherein said resistive shunt comprises a multistrand electrically conductive cable.

5. A vehicle according to claim 3, wherein said resistive shunt comprises at least a portion of a bus bar.

6. A vehicle according to claim 3, wherein said current sensing apparatus includes a printed-circuit board including an electrically conductive path broken at a break location;

and

a commercial current sensor coupled across said break in said current path, for generating said sensed signal representative of said motor current component; and

wherein

said resistive shunt comprises a further electrically conductive portion of said printed-circuit board.

7. A vehicle according to claim 3, wherein said current sensing apparatus is a noncontacting current sensing apparatus.

8. An arrangement for determining electrical current, said arrangement comprising;

a current sensing apparatus, said current sensing apparatus including a first electrical path through which a current to be sensed passes, said current sensing apparatus being capable of producing a sensed signal at a sensed signal port in linear response to the current in said first electrical path, at least up to a maximum value of said current in said first electrical path;

first and second terminals coupled to ends of said first electrical path, whereby said current sensing apparatus produces said sensed signal in response to current flowing between said first and second terminals; and

a second electrical path extending between said first and second terminals, said second electrical path being effectively in parallel with said first electrical path, so that a portion of the current flowing between said first and second terminals flows through said second electrical path rather than through said first electrical path, whereby the total current flowing between said first and second terminals is greater than the current flowing in said first electrical path, whereby said current sensing apparatus senses less than the total current flowing between said first and second terminals.

9. An arrangement according to claim 8, wherein said current sensing apparatus is noncontacting as between said first electrical path and sensed signal port.