Abstract: Disclosed is a system and method for controlling a clutch associated with a solenoid using a pulse width modulated (PWM) signal, which keeps the current through the coil constant over a wide temperature range and fluctuations in line voltage. The system may include a voltage source, a switch (such as a FET), a current sensor, and a processor. The system controls the clutch by sampling the voltage source, sampling the current measured by the current sensor, and computing a duty cycle, which is then used to generate a PWM control signal.

Abstract: A system and method of controlling motor temperature is based on computed motor power dissipation and a thermal model of the motor, rather than a measured motor temperature, in a control loop that limits the motor drive to prevent overheating. An ambient temperature sensor senses the ambient temperature near the motor, and a determination is made of the motor power dissipation. The motor winding temperature is estimated based on the sensed ambient temperature and the determined motor power dissipation. A maximum motor power dissipation that would raise the motor temperature to a predetermined maximum temperature value is determined based on the estimated temperature. The motor power dissipation is limited to a value that is below the determined maximum power dissipation.

Abstract: A coring bit, including an outer hollow coring shaft, and a rotationally uncoupled internal sleeve disposed inside the outer hollow coring shaft. The rotationally uncoupled internal sleeve may be a non-rotating internal sleeve. The rotationally uncoupled internal sleeve may be a free-floating internal sleeve.

Abstract: In a helical resonator, sometimes called a coaxial resonator with helical inner conductor, new capabilities are achieved by providing a double winding with the turns interspersed and of like pitch. One pair of respective opposite ends of the two portions of the double winding is connected directly to the cavity or ground conductor of the resonator, sometimes called the shield. Coupling to the cavity is achieved by any prior coupling technique. The new resonator can be included in compound helical resonator filters as would other helical resonators. One of the principal advantages of the new helical resonator is its ability to suppress odd harmonics both in its own resonator characteristic and in the characteristics of a composite filter in which it is only one of several helical resonators.