Apparatus for detecting direction of electric power flow

An apparatus comprising:

• a DC source of electric current;
• a motor capable of generating electric power;
• inverter means connected to said DC source for generating a pulsed supply voltage across said motor, and said motor having a motor current flowing in response to said pulsed supply voltage;
• at least one switch having contacts that close in response to said pulsed supply voltage turning on and open in response to said pulsed supply voltage turning off;
• at least one sense electric current substantially proportional to said motor current, and said sense electric current connected to flow through said contacts whereby the average electric current flow through said contacts is substantially proportional to an electric power flowing in said motor;
• a detector for detecting a sign of said power flowing in said motor and capable of generating an indicator signal responsive to said sign, said indicator signal having a first value when said power flows from said inverter into said motor and said indicator signal having a second value when power flows from said motor into said inverter.

An apparatus for measuring power flow through conductors connecting a load to a source of electric current, said load being capable of generating electric current, and said source of electric current being capable of accepting power flow from said load, comprising:

• said source generating a pulsed supply voltage across said load, and said load having a load current flowing in response to said pulsed supply voltage;
• at least one switch having contacts that close in response to said pulsed supply voltage turning on and open in response to said pulsed supply voltage turning off;
• and
• at least one sense electric current substantially proportional to said load current, and said sense electric current connected to flow through said contacts whereby the average electric current flow through said contacts is substantially proportional to an electric power flowing in said load.

An apparatus for measuring electric power flow in a three phase alternating current power line having a first conductor, a second conductor, and a third conductor, and supplied by a pulse width modulated voltage, comprising:

• a first current sensor (68A) responsive to current flow in said first conductor (10A);
• a first operational amplifier (70A) and a second operational amplifiers (70B), said first current sensor connected to a negative input terminal of said first operational amplifier and a positive input terminal of said second operational amplifier;
• a first electronic switch (72A) and a second electronic switch (72B),
• said first electronic switch (72A) having an input connected to an output of said first operational amplifier (70A), an output connected to a first end of a first resistor (84B1), and a control terminal (74A),
• said second electronic switch (72B) having an input connected to an output of said second operational amplifier (70B), an output connected to a first end of a second resistor (84B2), and a control terminal (74B),
• a second end of said first resistor (84B1) and a second end of said second resistor (84B2) connected to form a summation point (78);
• a first isolation amplifier (77A) having a first input connected to said first conductor (10A) and a second input connected to said second conductor (10B), and an output;
• a first comparator (76A) and a second comparator (76B), said output of said first isolation amplifier (77A) connected to a first input terminal of said first comparator (76A) and a first input terminal of said second comparator (76B), a second input terminal of said first comparator (76A) connected to a negative DC offset voltage and a second input terminal of said second comparator (76B) connected to a positive DC offset voltage, whereby said first comparator and said second comparator provide output logic signals indicative of the presence and polarity of voltage between said first conductor (10A) and said second conductor (10B);
• an output of said first comparator (76A) connected to said control terminal (74A) of said first electronic switch (72A), and an output of said second comparator (76B) connected to said control terminal (74B) of said second electronic switch (72B), thereby providing a first flutter switch wattmeter operating synchronously with said pulse width modulated voltage;
• a second current sensor (68C) responsive to current flow in said third conductor (10C);
• a third operational amplifier (86A) and a fourth operational amplifier (86B), said second current sensor connected to a negative input terminal of said third operational amplifier and a positive input terminal of said second operational amplifier;
• a third electronic switch (92A) and a fourth electronic switch (92B),
• said third electronic switch (92A) having an input connected to an output of said third operational amplifier (86A), an output connected to a first end of a third resistor (84B3), and a control terminal (90A),
• said fourth electronic switch (92B) having an input connected to an output of said fourth operational amplifier (86B), an output connected to a first end of a fourth resistor (84B4), and a control terminal (90B),
• a second end of said third resistor (84B3) and a second end of said fourth resistor (84B4) connected to said summation point (78);
• a second isolation amplifier (77B) having a first input connected to said second conductor (10B) and a second input connected to said third conductor (10C), and an output;
• a third comparator (88A) and a fourth comparator (88B), said output of said second isolation amplifier (77B) connected to a first input terminal of said third comparator (88A) and a first input terminal of said fourth comparator (88B), a second input terminal of said third comparator (88A) connected to a negative DC offset voltage and a second input terminal of said fourth comparator connected to a positive DC offset voltage, whereby said third comparator and said fourth comparator provide output logic signals indicative of the presence and polarity of voltage between said second conductor (10B) and said third conductor (10C);
• an output of said third comparator (88A) connected to said control terminal (90A) of said third electronic switch (92A), and an output of said fourth comparator (88B) connected to said control terminal (90B) of said fourth electronic switch (92B), thereby providing a second flutter switch wattmeter operating synchronously with said pulse width modulated voltage;
• and a voltage is developed at said summation point (78) substantially proportional to electric power flow in said three phase alternating current power line, and a sign of said voltage indicates a direction of flow of said electric power flow.