Motor driving device and vacuum pump

1. A motor driving device comprising:

an inverter having a plurality of switching elements for driving a motor;

an arithmetic section for calculating a rotational speed and a magnetic pole electric angle of a motor rotor based on information about a motor phase voltage and information about a motor phase current;

at least one low-pass filter for removing noise of at least one of the motor phase voltage and the motor phase current;

a delay correcting section for correcting a phase delay of the magnetic pole electric angle calculated by the arithmetic section so as to generate a corrected magnetic pole electric angle, the phase delay being predetermined based on filter characteristics of the at least one low-pass filter;

a driving command generating section for generating a sinusoidal wave driving command based on a difference between the rotational speed and a target rotational speed and the corrected magnetic pole electric angle; and

a PWM signal generating section for generating a PWM control signal for controlling on/off of the plurality of switching elements based on the sinusoidal wave driving command, wherein

the information about the motor phase voltage is a motor phase voltage detection signal input via a first low-pass filter included in the at least one low-pass filter, and the information about the motor phase current is a motor phase current detection signal input via a second low-pass filter included in the at least one low-pass filter,

filter characteristics of the second low-pass filter are set so as to be identical to filter characteristics of the first low-pass filter, and

the delay correcting section calculates a leading phase for correcting a phase delay caused by the filter characteristics of the first low-pass filter, and adds the leading phase to the magnetic pole electric angle so as to generate the corrected magnetic pole electric angle.

2. The motor driving device according to claim 1 , wherein

the delay correcting section calculates the leading phase according to the rotational speed calculated by the arithmetic section.

3. A motor driving device comprising:

an inverter having a plurality of switching elements for driving a motor;

an arithmetic section for calculating a rotational speed and a magnetic pole electric angle of a motor rotor based on information about a motor phase voltage and information about a motor phase current;

at least one low-pass filter for removing noise of at least one of the motor phase voltage and the motor phase current;

a delay correcting section for correcting a phase delay of the magnetic pole electric angle calculated by the arithmetic section so as to generate a corrected magnetic pole electric angle, the phase delay being predetermined based on filter characteristics of the at least one low-pass filter;

a driving command generating section for generating a sinusoidal wave driving command based on a difference between the rotational speed and a target rotational speed and the corrected magnetic pole electric angle; and

a PWM signal generating section for generating a PWM control signal for controlling on/off of the plurality of switching elements based on the sinusoidal wave driving command, wherein

the information about the motor phase current is a motor phase current detection signal input into the arithmetic section via a first low-pass filter included in the at least one low-pass filter,

the delay correcting section calculates a leading phase for correcting a phase delay caused by filter characteristics of the first low-pass filter, and adds the leading phase to the magnetic pole electric angle so as to generate the corrected magnetic pole electric angle,

the driving command generating section generates two-phase voltage commands Vd and Vq in a two-phase rotary coordinate system based on the difference, converts the two-phase voltage commands Vd and Vq into two-phase voltage commands vα and vβ in a two-phase fixed coordinate system based on the corrected magnetic pole electric angle, two-phase-to-three-phase converts the two-phase voltage commands vα and vβ so as to generate the three-phase voltage commands Vu, Vv and Vw, and generates the PWM control signal based on the three-phase voltage commands Vu, Vv and Vw, and

the arithmetic section calculates the rotational speed and the magnetic pole electric angle based on an estimated motor voltage obtained by delaying phase of the two-phase voltage commands vα and vβ in the two-phase fixed coordinate system by the same phase amount as the leading phase, and the motor current detection signal.

4. The motor driving device according to claim 3 , wherein

the delay correcting section calculates the leading phase according to the rotational speed calculated by the arithmetic section.

5. A motor driving device comprising:

an inverter having a plurality of switching elements for driving a motor;

an arithmetic section for calculating a rotational speed and a magnetic pole electric angle of a motor rotor based on information about a motor phase voltage and information about a motor phase current;

at least one low-pass filter for removing noise of at least one of the motor phase voltage and the motor phase current;

a delay correcting section for correcting a phase delay of the magnetic pole electric angle calculated by the arithmetic section so as to generate a corrected magnetic pole electric angle, the phase delay being predetermined based on filter characteristics of the at least one low-pass filter;

a driving command generating section for generating a sinusoidal wave driving command based on a difference between the rotational speed and a target rotational speed and the corrected magnetic pole electric angle;

a PWM signal generating section for generating a PWM control signal for controlling on/off of the plurality of switching elements based on the sinusoidal wave driving command;

a motor phase voltage detecting section for detecting a motor phase voltage;

a first low-pass filter included in the at least one low-pass filter for performing a low-pass filter process on a motor phase voltage detection signal output from the motor phase voltage detecting section;

a three-shunt type current detecting section for detecting a motor phase current through a shunt resistor provided to a ground side of the switching element of the inverter; and

a signal delay processing section for delaying a motor phase current detection signal that is output from the current detecting section and is analog-digital converted by a phase equivalent to the phase delay of the motor phase voltage detection signal through the first low-pass filter according to a digital process, wherein

the information about the motor phase voltage is the motor phase voltage detection signal that is analog-digital converted after the filter process is performed by the first low-pass filter,

the information about the motor phase current is a the phase corrected motor phase current detection signal that is output from the signal delay processing section, and

the delay correcting section calculates a leading phase for correcting the phase delay caused by the filter characteristics of the first low-pass filter, and adds the leading phase to the magnetic pole electric angle so as to generate the corrected magnetic pole electric angle.

6. The motor driving device according to claim 5 , wherein

the digital process is a low-pass filter process through a digital low-pass filter.

7. A vacuum pump comprising:

a pump rotor formed with an exhaust function section;

a motor for driving to rotate the pump rotor; and

the motor driving device according to claim 1 for driving the motor.