AC motor system with variable number of pole pairs for electric automobile

Abstract

The invention discloses an AC motor system with log of variable levels in an electric vehicle, which comprises an AC motor with log of variable levels, a level changing switch, a level changing controller, a speed sensor, and an electricity supplying unit including DC power and a frequency converter, wherein, the CD power supplies variable frequency AC through the frequency converter to provide electricity for the AC motor with log of variable levels; the level changing switch is used for switching the log of variable levels of the AC motor with log of variable levels; the speed sensor detects the rotational speed of the AC motor with log of variable levels and transfers a rotational speed signal to the level changing controller and then carries out on-off state of the level changing switch according to the rotational speed. By adopting the invention, the motor can keep reasonable dynamic characteristics constantly under different rotational speeds and reduce the extra weight and mechanical abrasion on a bodywork due to the application of a mechanical transmission.

Description

technical field [0001] The invention relates to an electric vehicle motor system, in particular to an AC motor system using pole-changing logarithms. Background technique [0002] The AC motor system of an existing electric vehicle generally uses an AC motor with a fixed number of pole pairs as power. In this way, it is difficult to ensure that the electric vehicle maintains appropriate dynamic characteristics in a large speed range from low speed to high speed. The reason is that for AC motors with the same power, at the same low speed, the low-speed torque with more pole pairs is greater than that with fewer pole pairs. When the speed reaches a certain speed, at the same high speed, the high-speed torque with a small number of pole pairs is greater than that with a large number of pole pairs. Such as figure 1 The N-M (speed-torque) curve of the AC asynchronous motor shown in the figure shows the N-M curve of the motor with 2 pairs of poles and 4 pairs of poles under the...

AI Technical Summary

Problems solved by technology

This fixed pole-pair number AC motor speed-torque characteristic cannot meet the power requirements of electric vehicles at different speeds

At present, a mechanical transmission is generally used for speed change control, which will increase the weight of the vehicle body and cause mechanical wear

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