A position of a rotor of a synchronous generator is measured under no load and under load. An angle of difference between where a terminal voltage crosses a zero-point and the marked position of the rotor under no load is calculated. A load angle is of the synchronous generator based the no load angle of difference and the load angle of difference.

The present invention relates to a motor driving apparatus and a refrigerator including the same. A motor driving apparatus according to an embodiment of the present invention comprises: a signal delay unit for delaying an input speed order signal; an inverter control unit for outputting an inverter switching control signal, on the basis of the speed order signal delayed by the signal delay unit; and an inverter for converting an input operation direct current power into a predetermined alternating current power, on the basis of a switching operation according to the inverter switching control signal, and driving a motor using the converted alternating current power. Therefore, it is possible to prevent starting failure and reduce noise.

A system, method, and computer-readable medium for determining the flow rate and fluid density in an electrical submersible pump (ESP) and controlling the ESP based on the flow rate and density. In one implementation, an ESP system includes an ESP, drive circuitry, a current sensor, a voltage sensor, and a processor. The ESP includes an electric motor. The drive circuitry is electrically coupled to the ESP and is configured to provide an electrical signal to power the ESP. The current sensor is configured to measure a current of the electrical signal. The voltage sensor is configured to measure a voltage of the electrical signal. The processor is configured to calculate speed of a shaft of the electric motor based on a frequency induced by rotation of the motor detected in the current. The processor is also configured to calculate a density of fluid in the ESP based on the speed.

A method reliably detects a field magnet position of a motor when starting a three-phase brushless motor that is driven according to PWM control with 120 energization, even when a power supply voltage fluctuates during sensing energization. An MPU 51 calculates a motor current Im according to Equation 1

[00001]$\begin{array}{cc}\mathrm{Im}=\mathrm{Vb}/\mathrm{Rm}\left(1-e^{\left(-\frac{Rm}{Lm}\right)}tb\right)& \mathrm{Equation}1\end{array}$ where inductance of the electric motor is Lm, a resistance value is Rm, a pre-fluctuation driving voltage is Vb, and an energization time is tb. The MPU 51 then substitutes the motor current Im found by Equation 1 and a post-fluctuation driving voltage Va into Equation 2 produced by solving Equation 1 for time to calculate a new energization time ta.

[00002]$\begin{array}{cc}ta=\left(\mathrm{Lm}/\mathrm{Rm}\right){\log }_e\left(-\mathrm{Va}/\mathrm{ImRm}-\mathrm{Va}\right)& \mathrm{Equation}2\end{array}$ Sensing energization is then performed for the energization time ta to specify the permanent magnetic field position.

A stepless regulation fan includes a fan main body, a main control circuit, a stepless regulation element electrically connected with the main control circuit and a first driving circuit. The fan main body is equipped with a first motor and fan blades connected to the first motor. The control circuit board integrates the main control circuit, a stepless regulation element electrically connected with the main control circuit and a first driving circuit. The stepless regulation element is configured for user operation. The first driving circuit is electrically connected to the first motor. The stepless regulation element includes an encoder switch, the encoder switch includes a first pin and a second pin, the first pin and the second pin are electrically connected with the main control circuit.

A stepless regulation fan includes a fan main body, a main control circuit, a stepless regulation element electrically connected with the main control circuit and a first driving circuit. The fan main body is equipped with a first motor and fan blades connected to the first motor. The control circuit board integrates the main control circuit, a stepless regulation element electrically connected with the main control circuit and a first driving circuit. The stepless regulation element is configured for user operation. The first driving circuit is electrically connected to the first motor. The stepless regulation element includes an encoder switch, the encoder switch includes a first pin and a second pin, the first pin and the second pin are electrically connected with the main control circuit.

In some examples, an apparatus includes a filter having first and second inputs, a current signal input, and an output. The apparatus also includes a speed observer having a voltage signal input, a current signal input, and an output, the output of the speed observer coupled to the second input of the filter. The apparatus also includes a ripple counter having an input and an output, the input of the ripple counter coupled to the output of the filter. The apparatus also includes a ripple processor having first and second inputs, and an output, the first input of the ripple processor coupled to the output of the ripple counter, the second input of the ripple processor coupled to the output of the speed observer, and the output of the ripple processor coupled to the first input of the filter.