ROBERT W NYSTROM
Radio and Television Technicians in Oxford, MA

5003252, Mar 26, 1991

Aug 16, 1989

7/394562

Robert W. Nystrom - Oxford MA

Load Controls Incorporated - Sturbridge MA

G01R 3102, G01R 2500

324158MG

An apparatus and method for sensing power factor and torque on the output of a variable frequency machine is disclosed. Initially, power is sensed in each phase of the three-phase machine by utilizing Hall generators for multiplying the phase current flowing through each phase by a current proportional to a phase voltage for each phase. The products are then summed to obtain a reading of the instantaneous power drawn by the three phase machine. The AC component is filtered out of the summed signal using a multistage filter which allows for maintaining a fast response time with low ripple. This output is divided by the speed of the machine and multiplied by a constant to result in a signal representing torque. For measuring power factor, power signal sensed in each phase is applied to a DC blocking capacitor, effectively separating the AC envelope proportional to voltage times current. The three signals are applied to absolute value amplifiers and summed to provide a signal yielding total power.

4764720, Aug 16, 1988

Jul 22, 1987

7/077009

Robert W. Nystrom - Oxford MA

Load Controls Incorporated - Sturbridge MA

G01R 2108, G01R 2114

324107

Disclosed is an apparatus and method for sensing power in a variable frequency machine. The power is sensed in each phase of the three phase machine by utilizing Hall generators for multiplying the phase current flowing through each phase by a current proportional to a phase voltage for each phase. The products are then summed to obtain a reading of the instantaneous power drawn by the three phase machine. The AC component is filtered out of the summed signal using a multi-stage filter which allows for maintaining of a fast response time with low ripple. In a preferred embodiment, a four stage filter utilizing R. C. filters is employed for this purpose.

D340698, Oct 26, 1993

Jul 31, 1991

7/738490

Robert W. Nystrom - Oxford MA

Load Controls, Incorporated - Sturbridge MA

D13162

5467012, Nov 14, 1995

May 10, 1994

8/240323

Robert W. Nystrom - Oxford MA

Load Controls Incorporated - Sturbridge MA

G06F 1546

324 74

Electrical power monitoring apparatus comprises a loop and a first conductor. A current sensor coupled to the first conductor provides a current signal that is representative of the current in the first conductor. A voltage sensor coupled at least to the first conductor provides a voltage signal that is representative of the voltage on the first conductor relative to that on a reference terminal. A multiplier coupled to the current sensor and voltage sensor has a power output which provides a power signal that is proportional to the instantaneous value of electrical power carried by the first conductor. A calibration circuit in the loop has an input coupled to the power output and has an adjustable output. A current regulator in the loop has an input coupled to the adjustable output to maintain the current in the loop between predetermined minimum and maximum loop current values.

5754421, May 19, 1998

Jul 7, 1995

8/499749

Robert W. Nystrom - Oxford MA

Load Controls, Incorporated - Sturbridge MA

H02M 510

363155

Electrical power monitoring apparatus comprises a loop and a first conductor. A current sensor coupled to the first conductor provides a current signal that is representative of the current in the first conductor. A voltage sensor coupled at least to the first conductor provides a voltage signal that is representative of the voltage on the first conductor relative to that on a reference terminal. A multiplier coupled to the current sensor and voltage sensor has a power output which provides a power signal that is proportional to the instantaneous value of electrical power carried by the first conductor. A calibration circuit in the loop has an input coupled to the power output and has an adjustable output. A current regulator in the loop has an input coupled to the adjustable output to maintain the current in the loop between predetermined minimum and maximum loop current values.

5930092, Jul 27, 1999

Jan 17, 1992

7/822063

Robert W. Nystrom - Oxford MA

Load Controls, Incorporated - Sturbridge MA

H02H 504

361 30

The electrical power to a device, such as a pump, is monitored by multiplying a current signal with a voltage signal to provide a power signal. Typically when the power signal is outside a predetermined range, power to the device is interrupted.