Device and method for determining motor rotor speed by using residual voltage of motor stator winding

Abstract

The invention discloses a device and a method for determining the rotating speed of a motor rotor by the residual voltage of a motor stator winding. The device comprises a microprocessor module, an input end of the microprocessor module is connected with a motor stator winding residual voltage detection circuit module, and the motor stator winding residual voltage detection circuit module comprises a voltage acquisition circuit module, a differential amplifier circuit module and a signal conditioning circuit module which are sequentially connected. The method includes the steps: firstly, acquiring and transmitting residual voltage signals of the motor stator winding; secondly, converting residual voltage line voltage signals UAB, UBC and UCA into residual voltage phase voltage signals UA, UB and UC, and performing Clark conversion to obtain a space phase angle phi j of a j group of residual voltage phase voltage space vectors; thirdly, performing linear fitting by the aid of a least square method to obtain a coefficient of a linear fitting straight-line equation; fourthly, determining the rotating speed of the motor rotor. The device is simple in structure, high in working stability and low in cost, and the residual voltage of the motor stator winding is effectively used.

Description

technical field [0001] The invention relates to a method for determining the rotational speed of a motor rotor, in particular to a device and method for determining the rotational speed of a motor rotor by using the residual voltage of the stator winding of the motor. Background technique [0002] As we all know, when an AC motor in normal operation suddenly loses the external power supply voltage, its rotor current will generate an induced voltage in the stator winding. The induced voltage does not decrease to zero immediately, but maintains for a certain period of time. This voltage is called the power-off residual voltage, or residual voltage for short. Power loss residual voltage is a common phenomenon in the use of AC motors. Due to the existence of residual voltage, it not only affects the motor, but also affects the stability of the power supply. Therefore, the residual voltage of AC motor power loss is harmful to both the motor and the power supply. of. However, th...

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Problems solved by technology

[0004] In the prior art, the detection of the motor rotor speed is usually carried out by using a speed sensor. On the one hand, it is necessary to add a speed sensor to the motor, which is not allowed in some occasions. On the other hand, the cost is high, and installation and use are not easy. It is convenient, and it does not make good use of the residual voltage of the motor stator winding

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