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PERFORMANCE CONTROLS, INC. ^® DHT-24 amplifier is a 3 phase motor drive that employs a proprietary Sensorless control algorithm to drive a Brushless DC motor (BLDC) that runs from a 24VDC input. However, perhaps the most important feature is that it does all this at 175C.

When operating thousands of feet below ground the last thing a service provider wants is to have their drill stop because of a component failure, particularly with the high financial and reputation costs associated with recovery. One of the most common failure modes for brushless motors when operating in a harsh down-hole environment is not the motor itself, but the feedback device. Halls are the most common choice for oil services tool applications because of size, but there are trade-offs in performance and reliability. A resolver can provide increased reliability, but they are often as large as the motor and add complexity to the drive electronics.

Down-hole services companies have been in search of a Sensorless solution because typical Sensorless motor drives have been unsatisfactory. The most significant drawback to Sensorless designs has been the high current needed to start a Sensorless motor, while power efficiency and performance are also important.

In response to these demands, Performance Controls has developed the DHT24-02.

Key features include:

• Sensorless – elimination of a feedback device from the motor increases system reliability
• Sinusoidal Commutation – A combination of advanced commutation and current control provide better bus voltage utilization, improved energy efficiency, and smoother operation compared with the industry standard - trapezoidal commutation
• Programmable Start-up Current Control – Parameters enable the OEM to set a current limit and ramp rate for the start-up routine
• High Temperature Operation - Independently tested for 175°C operation
• Ruggedization – The printed circuit board and components are designed and situated to survive the shock and vibration associated with down-hole services, such as MWD and LWD, and are ready to be potted into an OEM tool
• Small Size - 7" x 1.22"
• Control Loop – For pump applications, the drive can receive an analog signal from a pressure transducer and can be programmed to vary the speed as required
• Customization - PCI can modify the drive to make it compatible with an OEM's tool

A Sensorless drive is well suited for applications that do not require position control, have varying load, or require operation near zero speed. Therefore, a Sensorless drive is ideally suited for pump applications.

Additional benefits of Sensorless control include reduced system cost and size. The motor cost is reduced because of the removal of the feedback device and the further reduction of material and labor associated with the wiring of the feedback device. The reduction of wiring also reduces the space required to install the drive system.