High dv/dt from the emerging SiC variable-frequency drives can easily induce overvoltage across the motor stator winding terminals, especially for long-cable-connected and high-voltage motor-drive systems. Due to the fast switching speed and surge impedance mismatch between cables and motors, this overvoltage can be two times or even higher than the DC-bus voltage of the inverter, resulting in motor insulation degradation or irreversible breakdown. The most common solution to mitigate such overvoltage is to install a dv/dt or a sinewave filter at the output of the drive, which decreases the efficiency and power density of the system. Among different stator coils, the first one (close to the drive side) is the most susceptible to insulation breakdown since it experiences higher overvoltage than the others due to the nonlinear distribution of the reflected surge voltages. In this paper, an innovative high-efficiency ultracompact mitigation solution is introduced, which is a tiny auxiliary circuit embedded inside the motor stator (or at the motor terminal box), specifically across the first few coils of each phase (i.e., smart coils). The proposed smart coil circuit effectively mitigates the surge overvoltage, which can be scalable to any type of motor-drive systems, regardless of cable length and semiconductor rise time. The proposed solution can dramatically improve the reliability, efficiency, and power density of motor-drive systems.
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Empirical Characterization of a High-performance Exterior-rotor Type Brushless DC Motor and Drive
Recently, brushless motors with especially high torque densities have been developed for applications in autonomous aerial vehicles (i.e. drones), which usually employ exterior rotortype geometries (ER-BLDC motors). These motors are promising for other applications, such as humanoids and wearable robots; however, the emerging companies that produce motors for drone applications do not typically provide adequate technical specifications that would permit their general use across robotics-for example, the specifications are often tested in unrealistic forced convection environments, or are drone-specific, such as thrust efficiency. Furthermore, the high magnetic pole count in many ER-BLDC motors restricts the brushless drives able to efficiently commutate these motors at speeds needed for lightly-geared operation. This paper provides an empirical characterization of a popular ER-BLDC motor and a new brushless drive, which includes efficiencies of the motor across different power regimes, identification of the motor transfer function coefficients, thermal response properties, and closed loop control performance in the time and frequency domains. The intent of this work is to serve as a benchmark and reference for other researchers seeking to utilize these exciting and emerging motor geometries.
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- Award ID(s):
- 1760247
- NSF-PAR ID:
- 10297861
- Date Published:
- Journal Name:
- Proceedings of the IEEE Conference of Intelligent Robots and Systems
- Page Range / eLocation ID:
- 8018 to 8025
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1109/IROS40897.2019.8967626
