In recent years, with the wide application of machine room free and small machine room elevator, gearless transmission of permanent magnet synchronous motor has become the main trend of elevator industry technology development. The gearless elevator is directly connected with the traction wheel of the main engine by the output shaft of the motor, and directly drives the elevator to run without gear reduction or other reduction mechanism. This transmission mode has the characteristics of high transmission efficiency, low noise and simple mechanical structure, and is a better scheme among many traction transmission modes of elevator. At present, most elevator products are driven by frequency conversion, from the traditional gearless elevator to permanent magnet synchronous motor gearless elevator, there are those different and requirements in frequency conversion control, which is the problem to be discussed in this paper. 

Since it is direct traction without gear reduction, the response of the motor will be directly acted on the elevator car through the wire rope. Therefore, in order to consider the vibration and comfort of the elevator, it is necessary to design a high-performance frequency conversion controller with high control accuracy and fast response speed. In particular, the detection accuracy of current loop and the speed of calculation response. 

In the control system of permanent magnet synchronous motor, the encoder not only feeds back the speed of the motor, but also needs to detect the magnetic pole position of the motor, so the encoder needs to be able to feedback the magnetic pole position signal. In addition, the gearless traction mode, the motor speed is low, so the encoder is required to have a higher resolution, generally required above 4096C/T to make the system has good control performance. So this kind of elevator system will generally choose positive and cosine high performance rotary encoder. At present, the standard configuration of inverter is incremental rotary encoder of A and B phases, which requires that the interface and application design of new rotary encoder should be considered in the design of inverter. 

In order to ensure that the elevator can obtain better starting and braking characteristics under various load conditions, it is necessary to set up a load detection device in the gearless traction drive control system. In the system, as mentioned above, the high performance rotary encoder of sine and cosine is used. The design of frequency converter can make use of the performance of rotary encoder to calculate the torque to be compensated at the moment of elevator starting, and compensate the input and output torque, so as to achieve smooth starting. This requires the frequency converter in signal detection accuracy, anti-interference ability and computational response speed have a certain degree of improvement. 

Noise The traditional elevator system, because of the use of a gearbox transmission mode, so the noise of the elevator room is generally based on the noise of the gearbox. In the gearless elevator with permanent magnet synchronous motor, the electromagnetic noise of the motor becomes the main component of the noise in the elevator room because there is no gear reducer. So the system for inverter in the motor noise control also put forward higher requirements. 

In the design and production of elevator, the development and application of permanent magnet synchronous motor, as the traction motor of elevator, is a technological progress. Its advantages are as follows: simple and compact structure, less maintenance; High safety and reliability; Low noise pollution to the environment, no oil pollution, and can improve the power factor, is the ideal environmental protection products; Improve mechanical transmission efficiency, use energy saving, economic, with high cost performance; Compared with the ac gearless asynchronous motor drive system, the advantages of low speed, speed, hard mechanical characteristics and shutdown are unmatched by the asynchronous motor; Compared with dc gearless motor drive system, it has higher low speed performance, speed regulation accuracy, fast response performance, and long life, less power consumption, simple maintenance; In addition, it is easy to realize the ideal driving model of low speed and large torque.