Operating method (10) for a compressor (101) of a refrigerating machine (100), said compressor (101) comprising an electric motor (102) and a power supply device (103) configured to modulate a supply voltage (V) and/or current (I) and/or frequency (F) for driving said electric motor (102), said method (10) being characterized in that it involves: —setting (A) a stator resistance calibration N value (Ro) and at least one threshold value (S1, S2, S3, S4) for a control parameter (R), said threshold value (S1, S2, S3, S4) being correlated to said calibration value (Ro); —injecting (B), continuously during operation of said electric motor (102), a disturbance signal (V1, I1) into said electric motor (102) by means of said power supply device (103), said disturbance signal (V1, I1) consisting of a disturbance of said supply voltage (V) and/or current (I); detecting (C) f by means of voltage and current measurements at the phases of said electric motor (102), a resulting voltage signal (V2) and a resulting current signal (I2), corresponding to said perturbation signal (V1, I1); —associating (D) with said control parameter (R) a value calculated as a function of said resulting voltage signal (V2) and a resulting current signal (I2); —regulating or interrupting (E) said supply voltage (V) and/or current (I) and/or frequency (F) depending on said control parameter (R) with respect to said at least one threshold value (S1, S2, S3, S4).

A variable speed drive (VSD) can be used to vary the voltage-to-frequency ratio (V/f) supplied to a compressor motor of a heating, ventilation, air conditioning or refrigeration (HVAC&R) system to make the motor stronger or weaker to compensate for varying conditions in the HVAC&R system. The VSD and corresponding control system or algorithm can monitor an operating parameter of the HVAC&R system, such as the kW absorbed by the motor, and then raise or lower the V/f of the VSD to obtain the lowest possible power consumption from the motor.

A method is provided for braking a compressor of a refrigeration appliance, of an air conditioning appliance or of a heat pump in which the compressor has a brushless motor with windings and a controller for braking the motor. The controller is configured to brake the brushless motor by using a braking current in a controlled manner starting from an operating rotational speed, in which the braking current during the controlled braking is dependent on induced voltages determined before the controlled braking. The method for braking includes rotating the motor at an operating rotational speed, receiving a signal for decelerating, braking or slowing down, determining voltages induced in the windings and supplying a braking current having a decreasing frequency to the windings, in which the braking current during the braking is dependent on the previously determined induced voltages. A compressor and a refrigeration appliance having the compressor are also provided.

A method for correcting pump model includes: obtaining a pump model for a pump, the pump model including a Q-P curve and a Q-H curve at each of a plurality of frequencies; at each frequency, determining a power error based on a zero-flow-rate power or an actual operating point of the pump under one of the frequencies; and determining a corrected pump model based on the pump model and the power error. The determination of the corrected pump model includes: at each frequency, determining a corrected Q-P curve to be the Q-P curve shifted by the power error; determining a Q-H-P surface based on the corrected Q-P curves and the Q-H curves at all the frequencies; at each frequency, determining a head error based on the surface and the power error; and at each frequency, determining a corrected Q-H curve to be the Q-H curve shifted by the head error.

A method for operating a variable capacity drive circuit of a compressor includes operating first and second four-quadrant switches in a first state in which the first four-quadrant switch is closed and the second four-quadrant switch is open such that a voltage seen by the motor is equal to an AC line voltage. The method also includes operating the first and second four-quadrant switches in a second state where the first four-quadrant switch is open and the second four-quadrant switch is closed such that the voltage seen by the motor is to zero. Further, the method includes providing a positive firing angle and a negative firing angle for defining when the first and second four-quadrant switches are operated in each of the first and second states. Moreover, the method also includes transitioning between the first and second states using the firing angles at a switching frequency determined by the AC line voltage frequency.

In some implementations, a controller may obtain a setting for a maximum discharge pressure associated with a fluid pump that is to be allowed during a hydraulic fracturing operation. The fluid pump may be driven by a motor that is controlled by a variable frequency drive (VFD). The controller may determine a maximum torque for the motor that achieves the maximum discharge pressure. The controller may cause, via the VFD, adjustment to a speed of the motor to maintain a torque of the motor at or below the maximum torque for the motor.

In some implementations, a controller may obtain a setting for a target discharge pressure associated with a fluid pump driven by a motor that is controlled by a variable frequency drive (VFD). The target discharge pressure may be for use in a pressure test of a system that includes the fluid pump. The controller may determine a target torque for the motor that achieves the target discharge pressure. The controller may cause, via the VFD and in connection with the pressure test, adjustment to a speed of the motor to achieve the target torque for the motor.

A system, method, and computer-readable medium for determining the flow rate and fluid density in an electrical submersible pump (ESP) and controlling the ESP based on the flow rate and density. In one implementation, an ESP system includes an ESP, drive circuitry, a current sensor, a voltage sensor, and a processor. The ESP includes an electric motor. The drive circuitry is electrically coupled to the ESP and is configured to provide an electrical signal to power the ESP. The current sensor is configured to measure a current of the electrical signal. The voltage sensor is configured to measure a voltage of the electrical signal. The processor is configured to calculate speed of a shaft of the electric motor based on a frequency induced by rotation of the motor detected in the current. The processor is also configured to calculate a density of fluid in the ESP based on the speed.

Disclosed are a variable capacity compressor operation mode determination method and device, a variable capacity compressor and an air conditioner. The variable capacity compressor operation mode determination method includes: detecting a current value of a compressor at present as A1 before switching an operation mode of the compressor; detecting the current value of the compressor at present as A2 after switching the operation mode of the compressor and reaching a preset time; comparing A1 and A2, determining that the switching of the operation mode of the compressor is successful when a ratio relationship between A1 and A2 satisfies a preset condition, and determining that switching of the operation mode of the compressor is failed when the ratio relationship between A1 and A2 dissatisfies a preset condition.

A controller that is associated with a pump system causes a power ramp rate of a motor of the pump system to have an initial power ramp rate. The controller monitors, after causing the power ramp rate of the motor to have the initial power ramp rate, a frequency of a power bus. One or more power sources provide power to the pump system via the power bus. The controller causes, based on monitoring the frequency of the power bus, the power ramp rate of the motor to be modified.