Electronic relay for calculating the power of a multiphase electric load based on a rectified wave signal and a phase current

• US 5,777,833 A
• Filed: 01/24/1997
• Issued: 07/07/1998
• Est. Priority Date: 02/02/1996
• Status: Expired due to Fees

• Current Assignee: Schneider Electric SA (Schneider Electric SE)
• Original Assignee: Schneider Electric SA (Schneider Electric SE)
• Inventors: Romillon, Jean-Marc
• Primary Examiner(s): Gaffin, Jeffrey A.
• Assistant Examiner(s): SHERRY, MICHAEL JUDE
• Application Number:
  US08/789,181
• Time in Patent Office: 529 Days
• Field of Search: 361/23-31, 361/78, 361/79, 361/83, 361/85-87, 361/93-94, 361/187, 363/50, 363/74, 363/76, 318/729, 364/483, 364/492
• US Class Current: 361/30
• CPC Class Codes: G01R 19/252 using analogue/digital converters of the type with conversion of voltage or current into frequency and measuring of this frequency
• CPC Class Codes: H02H 3/382 involving phase comparison between current and voltage or between values derived from current and voltage
• CPC Class Codes: H02H 7/0822 Integrated protection, motor control centres

Abstract

An electronic relay having a current sensor device (C1, C2, C3), logic inputs (3) and an electronic circuit (4) provided with processing means capable of calculating, from the current signal (I) supplied by the current sensor device and a rectified voltage signal (V) supplied by one of the logic inputs, the value of the power factor of the motor (cosφ) and/or the value of the power supply voltage (U) of the motor.

Claims

1. An electronic relay for a multiphase electric load, said electronic relay comprising:

a plurality of sensor devices that supply a phase current for each phase;

a threshold voltage rectifying circuit that receives an alternating supply signal and outputs a rectified signal having a period, a minimum voltage condition, and a maximum voltage condition; and

a microcontroller circuit that calculates a power factor or a power supply voltage that is a function of

at least one of the phase currents and

the period of the rectified signal.

2. The electronic relay according to claim 1, wherein the microcontroller circuit calculates

the period of the rectified signal and

the time during which the rectified signal is in a minimum voltage condition.

3. The electronic relay according to claim 2, wherein the microcontroller circuit calculates

the time passing between an instant at which the at least one of the phase currents passes through zero intensity and an instant at which the rectified signal passes from the minimum voltage condition to the maximum voltage condition and

the phase shift between the at least one of the phase currents and the alternating supply signal, said phase shift between the at least one of the phase currents and the alternating supply signal is a function of

the time passing between the instant at which the at least one of the phase currents passes through zero intensity and the instant at which the rectified signal passes from the minimum voltage condition to the maximum voltage condition,

the period of the rectified signal, and

the time during which the rectified signal is in the minimum voltage condition.

4. The electronic relay according to claim 3, wherein the microcontroller circuit calculates the power factor from

the phase shift between the at least one of the phase currents and the alternating supply signal and

a table defining a correlation between phase shift values and associated cosine values.

5. An electronic relay circuit according to claim 2, wherein the microcontroller circuit calculates the power supply voltage from a voltage coefficient that is a function of

the period of the rectified signal and

the time during which the rectified signal is in the minimum voltage condition.

6. The electronic relay circuit according to claim 5, wherein the power supply voltage is also calculated from a table of values defining a correlation between voltage coefficient values and associated voltage values.

7. The electronic relay according to claim 5, wherein the power supply voltage is represented by a refining function having a director coefficient equal to the voltage coefficient.