A motor drive apparatus that can continue operation within the upper limit of system control even if a voltage drop of an AC power source occurs during operation of a motor used for a hoist or a crane is provided. The inverter control unit of the motor drive apparatus includes a speed reference setting means for setting the rotation speed of the motor, means for detecting a speed deviation between the output of the rotation speed detection means for detecting the rotation speed of the motor and the output of the speed reference setting means, means for controlling the output current of the inverter according to the output of the speed deviation. The speed reference setting means includes a correction circuit for correcting an external speed command given from outside. The correction circuit corrects the external speed command according to a deviation between a detection value of a DC voltage and a first reference value when a voltage drop signal is received from the voltage drop detection means, and makes the corrected speed command as the output of the speed reference setting means.

A system comprises an electric submersible pump (ESP) motor electrically coupled to a variable speed drive (VSD) that outputs voltage to the ESP motor. The system comprises a magnet on a shaft of the ESP motor and a downhole sensor coupled to the magnet, wherein the downhole sensor is to measure a magnetic flux of the magnet. The system comprises a VSD controller to control the VSD, wherein the VSD controller comprises a processor and a non-transitory memory storage having instructions stored thereon that are executable by the processor to perform operations comprising: obtaining a measurement of at least one pump performance variable and a motor current for a first period of time to establish a first data set and making a first adjustment to a voltage output from the VSD to the ESP motor, the first adjustment having a first adjustment type.

Disclosed are exemplary embodiments of systems and methods for controlling inducer motor speed. In an exemplary embodiment, a method includes changing stator voltage of an inducer motor (e.g., by changing a firing angle of a triac, using a transistor, a silicon controlled rectifier or semiconductor controlled rectifier (SCR), other switching device, etc.); determining actual inducer motor speed (e.g., by using a hall effect sensor or other speed sensor, etc.); and after determining the actual inducer motor speed, changing the motor stator voltage (e.g., by changing the firing angle of the triac, etc.) to a value at which the actual inducer motor speed is controllably regulated and/or maintained substantially at a set speed.

An electric motor system is described. The electric motor system includes a drive circuit including an inverter configured to supply variable frequency current and a contactor configured to supply line frequency current. The electric motor system also includes an electric motor coupled to the drive circuit wherein the electric motor is communicatively coupled to a controller. The controller is configured to control the inverter to supply variable frequency current to the electric motor, thereby operating the electric motor at a motor speed, and determine, based upon at least one input parameter, a maximum potential motor speed the inverter can achieve. The controller is also configured to receive a command to operate the electric motor at line frequency current and control the drive circuit to transition from supplying variable frequency current to supplying line frequency current before the maximum potential motor speed the inverter can achieve is reached.

The invention relates to a method for controlling a three-phase inverter (3) using a 120° control arrangement associated with a PWM-type control, the inverter (3) being driven by a controller and configured to power a permanent-magnet synchronous motor (5) of a device on board an aircraft. The motor (5) comprises a stator and a rotor that can be rotated relative to the stator when the motor (5) is powered. The inverter (3) comprises three branches (31, 32, 33), each branch comprising two switches (310, 311, 320, 321 and 330, 331) associated with a motor winding sing a 120° control arrangement of a three-phase inverter. The method is characterised in that when one switch on one branch is controlled such as to switch front the on-state to the off-state, the other switch on said branch is controlled such as to be in the on-state for a sufficient amount of time to allow the magnetic discharge of the motor winding associated with said branch.

The invention relates to fluid drive systems used in fluid wells and brake systems for permanent magnet wellhead direct drives. The braking controller connects or disconnects a brake resistor from a back EMF. A variable frequency drive (VFD) drives the motor and communicates with the control circuitry of the brake controller. The control circuitry monitors the brake resistor and depending on the rotational speed and direction of the motor and operating state of the VFD, disconnects or connects the brake resistor. If the direction of the motor is in reverse and above a threshold speed, it connects the brake resistor. If the direction of the motor is in reverse and below the threshold speed, the control circuitry dissipates stored back EMF through the brake controller. The amount of stored back EMF corresponds to the time to empty a pump.

Disclosed are exemplary embodiments of systems and methods for controlling inducer motor speed. In an exemplary embodiment, a method includes changing stator voltage of an inducer motor (e.g., by changing a firing angle of a triac, using a transistor, a silicon controlled rectifier or semiconductor controlled rectifier (SCR), other switching device, etc.); determining actual inducer motor speed (e.g., by using a hall effect sensor or other speed sensor, etc.); and after determining the actual inducer motor speed, changing the motor stator voltage (e.g., by changing the firing angle of the triac, etc.) to a value at which the actual inducer motor speed is controllably regulated and/or maintained substantially at a set speed.

A method comprises operating an electric submersible pump (ESP) motor downhole in a well. The ESP motor is electrically connected to a variable speed drive (VSD) proximate to the well. The operating comprises measuring a revolution rate and a motor current of the ESP motor for a first period of time and performing a first adjustment of a voltage output of the VSD. The method comprises measuring, after the first adjustment, the revolution rate and the motor current of the ESP motor for a second period of time determining a difference between the motor current measured for the first period of time and the motor current measured for the second period of time; and performing a second adjustment of the voltage output of the VSD based on a change in the revolution rate and the motor current between the first period of time and the second period of time.

A method of setting up an electrical motor speed control in a fluidic system including a turbomachine, an electric motor having a number p of pole pairs rotating the turbomachine, a variable speed drive controlling the speed of the electric motor, a sensor measuring a parameter H, Q of the turbomachine, and a system controller receiving the sensor's measurements and controlling the operation of the fluidic system. The method includes driving the electric motor at a predetermined electrical frequency, Fe, such that the turbomachine rotates with a controlled rotational speed N, determining the point of intersection of the system curve of the fluidic system and of the performance curve of the turbomachine to obtain the turbomachine's nominal operating point, and thus the nominal value, Hn, Qn, of the turbomachine parameter, measuring, with the sensor, the current value, H, Q of the turbomachine parameter, calculating the controlled rotational speed N by inputting, into the Affinity Laws, the determined nominal value, Hn, Qn, the measured current value, H, Q, and the known nominal rotational speed, Nn, of the turbomachine, determining the number p of pole pairs of the electric motor based on the ratio of the electrical frequency Fe and the calculated controlled rotational speed N, and adapting the setup of the variable speed drive to match the determined number p of pole pairs.

An electric motor system is described. The electric motor system includes a drive circuit including an inverter configured to supply variable frequency current and a contactor configured to supply line frequency current. The electric motor system also includes an electric motor coupled to the drive circuit wherein the electric motor is communicatively coupled to a controller. The controller is configured to control the inverter to supply variable frequency current to the electric motor, thereby operating the electric motor at a motor speed, and determine, based upon at least one input parameter, a maximum potential motor speed the inverter can achieve. The controller is also configured to receive a command to operate the electric motor at line frequency current and control the drive circuit to transition from supplying variably frequency current to supplying line frequency current before the maximum potential motor speed the inverter can achieve is reached.