Abstract: 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.

Abstract: A shear coupler provides a breakable connection between adjacent members of a pump rod string. The coupler features an elongated shear stud, a hollow member in which the shear stud is axially received, a first set of rotational locking features externally defined on the shear member for engagement with a first set of matable rotational locking features internally defined on the hollow member; and a second set of rotational locking features externally defined on the shear member for engagement thereof with a second set of matable rotational locking features internally defined on the hollow member. The first and second sets of rotational locking features of the shear member are disposed on opposite sides of a weakened area thereof, and tensile and torsional loads on the coupler are substantially isolated from one another. Methods and equipment for applying torsional and tensile pre-loads to the coupler are also provided.

Abstract: 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.

Abstract: A shear coupler provides a breakable connection between adjacent members of a pump rod string. The coupler features an elongated shear stud, a hollow member in which the shear stud is axially received, a first set of rotational locking features externally defined on the shear member for engagement with a first set of matable rotational locking features internally defined on the hollow member; and a second set of rotational locking features externally defined on the shear member for engagement thereof with a second set of matable rotational locking features internally defined on the hollow member. The first and second sets of rotational locking features of the shear member are disposed on opposite sides of a weakened area thereof, and tensile and torsional loads on the coupler are substantially isolated from one another. Methods and equipment for applying torsional and tensile pre-loads to the coupler are also provided.