Abstract: A system for determining electrical characteristics of an electric load can comprise a signal modulation circuit that can include a first integral controller configured to control AC reference voltage based on a requested maximum AC current and an estimated maximum AC current, a second integral controller configured to control DC reference voltage based on a requested DC current and an estimated DC current, a signal demodulation circuit including an AC current estimation circuit configured to generate the estimated maximum AC current for the signal modulation circuit, a DC current estimation circuit configured to generate the estimated DC current for the signal modulation circuit, and a resistance and inductance (RL) estimation circuit configured to determine inductance of the electric load based on the estimated maximum AC current and phase shift, wherein the estimated maximum AC current is a value lower than a DC offset current value.

Abstract: A system for determining electrical characteristics of an electric load can comprise a signal modulation circuit that can include a first integral controller configured to control AC reference voltage based on a requested maximum AC current and an estimated maximum AC current, a second integral controller configured to control DC reference voltage based on a requested DC current and an estimated DC current, a signal demodulation circuit including an AC current estimation circuit configured to generate the estimated maximum AC current for the signal modulation circuit, a DC current estimation circuit configured to generate the estimated DC current for the signal modulation circuit, and a resistance and inductance (RL) estimation circuit configured to determine inductance of the electric load based on the estimated maximum AC current and phase shift, wherein the estimated maximum AC current is a value lower than a DC offset current value.

Abstract: Apparatus (103) suitable for determining the resistance and inductance of an electric motor (101) estimates the phase shift between a voltage applied to the motor and motor current. Estimation of the phase shift employs a heterodyne technique. The measured motor current is conditioned prior to heterodyning in a mixer 203 in order to reduce the effects of nonlinearities introduced by a voltage source inverter (102) which supplies the motor (101) with a voltage. A value for impedance may be calculated as a ratio of a voltage applied to the motor and the motor current. The resistance and inductance may then be calculated from the impedance and phase shift calculations. In cases where the voltage applied to the motor cannot be directly measured but only the voltage supply to the voltage source inverter 102 is known, a value for impedance may be determined based on a ratio of a reconstructed voltage signal having a phase angle equal to that of the motor current and the motor current.

Abstract: Apparatus (103) suitable for determining the resistance and inductance of an electric motor (101) estimates the phase shift between a voltage applied to the motor and motor current. Estimation of the phase shift employs a heterodyne technique. The measured motor current is conditioned prior to heterodyning in a mixer 203 in order to reduce the effects of nonlinearities introduced by a voltage source inverter (102) which supplies the motor (101) with a voltage. A value for impedance may be calculated as a ratio of a voltage applied to the motor and the motor current. The resistance and inductance may then be calculated from the impedance and phase shift calculations. In cases where the voltage applied to the motor cannot be directly measured but only the voltage supply to the voltage source inverter 102 is known, a value for impedance may be determined based on a ratio of a reconstructed voltage signal having a phase angle equal to that of the motor current and the motor current.