摘要:
Rotational electric machine stator winding arrangement characterized, inter alia, by at least one coil of each parallel circuit being discontinuous with the other coils of the corresponding circuit, and by coils configured to accept phase voltage not being adjacent coils having a point at the lowest potential of a corresponding circuit.
摘要:
A method of servicing a wellbore comprising placing a cement composition comprising a cementitious material, water, and an elastomeric material comprising a bonding polar group into a wellbore, and allowing the cement composition to set to form a set cement, wherein the elastomeric material has a phase transition temperature, exhibits cold flow behavior, or both at less than or equal to the bottom hole static temperature of the wellbore. A method of servicing a cased wellbore penetrating a formation, comprising introducing a self-repairing cementitious material into a wellbore, and allowing the cement to set, wherein upon a loss of structural integrity the set cement self-repairs, and wherein the loss of structural integrity comprises the formation of flow pathways for fluid migration in the cement and self-repair comprises obstructing potential pathways for fluid migration.
摘要:
An electrical machine drive system (100) includes a DC power source (102), an inverter (104) and a three-phase electrical machine (106). In response to a fault condition, power switches (122, 124) in the inverter are opened. Any short circuits are then determined by examining the phase currents of the three-phase electrical machine. If short circuits are found in the inverter, then the inverter is made balanced by shorting all upper braches (122, 126) or all lower branches (124, 128), depending on the location of the short circuit. Torque ripples are avoided by balancing the circuit during the fault mode, thereby providing comfort to a user of an electric or hybrid electric vehicle employing the electrical machine drive system.
摘要:
A new class of doubly-salient machines which incorporates a specific stator/rotor pole arrangement to provide a linearly increasing flux linkage over the entire area of pole overlap, and either (1) stationary permanent magnets mounted in the stator, or (2) one or more auxiliary field windings coiled about the stator or (3) a combination of stationary permanent magnets and auxiliary field windings. In each of the three cases, the permanent magnets or auxiliary winding(s) generate the primary flux and block and thereby limit flux in the ordinary path of the secondary flux (due to the stator windings) through the stator. The altered magnetic structure utilizing four stator and six rotor poles increases efficiency when operated as a generator, and provides greater output torque when operated as a motor.
摘要:
A device for field weakening in a doubly-salient variable reluctance motor having permanent magnets in the stator. The field weakening increases the constant power range of the motor and is accomplished by controlled movement of steel insets toward and away from the sides of the stator proximate the permanent magnets to provide a controllable by-pass flux path thereabout. Alternatively, the field weakening may be accomplished by a flux by-pass collar which may be angularly positioned around the stator to bridge the permanent magnets of the motor with discrete magnetic sections, thereby providing an alternate by-pass flux path around the permanent magnets in addition to the main air gap flux path. A third alternative means for maintaining a constant power range is accomplished by controlled axial sliding of the permanent magnets themselves into and out from the stator.
摘要:
Methods of treating subterranean formations comprising providing a wellbore in a subterranean formation having at least one fracture therein; providing a first treatment fluid comprising a base fluid and an acid generating inert agent; providing a second treatment fluid comprising a base fluid, and an acid generating activator; introducing the first treatment fluid into the at least one fracture; and introducing the second treatment fluid into the at least one fracture, wherein the acid generating inert agent in the first treatment fluid reacts with the acid generating activator in the second treatment fluid so as to generate an acid in the at least one fracture and create or enhance at least one microfracture therein.