Commutation Spark Research Articles

Design and research of deep slot universal motor for electric power tools

In this paper, a deep slot universal motor is designed for electric power tools. The deep slot structure can reduce the cost of universal motor materials and improve production efficiency. A mathematical model of a universal motor is established and a simulation model is established by MagNet finite element software. Then, the static magnetic field distribution and load characteristics of the deep slot universal motor are analyzed. Different methods are adopted to improve the commutation spark of a deep slot universal motor. Finally, three 550-W and 9500-rpm prototype motors are tested. Simulation and experimental results indicate that an uneven air gap, brush offset by a certain angle, as well as different turns of the lead coil and the lag coil can effectively improve the commutation spark of a deep slot universal motor.

Commutation Sparking Image Monitoring for DC Motor

As one of the most important parameters in evaluating the status of a DC motor, commutation spark has been widely used in condition monitoring and fault diagnosis. A new approach using image processing techniques on the commutation spark has been proposed. Advantageous over other methods using partial spark information, the details about the motor condition can be comprehensively retained and extracted from the sparking images. The sparking images were obtained by the cameras, which were fixed at the certain sites in DC motor beforehand. The images were processed through the sparking image preprocessing, segmentation, enhancement, and feature extraction. Comparing the characteristic parameters of the sparking image with the result of the subjective grading, the relationship between the parameters and the sparking grades had been analyzed to monitor the DC motor. The effectiveness had been demonstrated by application examples.

Basic Studies for Accurate Commutation Analysis which Enables Commutation Spark Energy Estimation

DC machine has been used in steel industries and paper industries, Owing to their advantages for adjustable speed drive. The design objective for DC machines is to increase their output power and decrease their size and weight, though DC machines have more than 100 years of application history. Commutation is one of the most important for phenomenon which determines machine reliability, when the design objective is required in design stage. In other words, the commutation is an armature coil current reversing process, in commutation where the coil is short circuited by brush. In this paper the “Equivalent commutation circuit which is well known is applied to analyze the commutation process in this field. If the reversing process is retarded commutation spark may accrue at leaving edge of the brush and commutation failure may be caused.

B119 高速度カメラによる小形モータの整流火花の撮影

We have done some attempts to understand the mechanism of commutation spark generation in universal motor from the image aspect using a high-speed camera. We have also mentioned about the generation of single and plural number of sparks at one commutator segment and the voltage between brush and commutator segment. The commutation sparks of the motor are generated with a sliding contact between brush and commutator segment in the moment that the segment is separated from the brush. And the width of the brush is just 10mm, this time, we were able to clarify position of the brush which sparks are generated and the relation between positive brush and negative brush.

Unraveling the Image of Commutation Spark Generated in Universal Motors

A universal motor, which is mainly used in vacuum cleaners, generates commutation sparks at the moment when the brush and the commutator segment are separated from each other during rotation. This study investigates the mechanism of commutation spark generation by analyzing high-speed camera images and its electrical aspect. We invented a new external trigger method that used laser light as the trigger signal for the shuttering a high-speed camera. This method enabled us to photograph sparks on any desired commutator segments during high-speed rotation, and that made the analysis after photographing easier. This paper shows that commutation sparks in universal motors are generated on every other commutator segment and at the peak of pulses in the voltage between the brush and commutator segment. Other aspects are also clarified, such as the generation of the singular and plural number of sparks on one commutator segment at a time, the time from the moment of spark generation to extinction, and spark generation during a single rotation.

The Distribution of Commutation Sparks in Universal Motors

We have done some attempts to understand the mechanism of commutation spark generation in universal motor from the image aspect using a high-speed camera. We have also mentioned about the generation of single and plural number of sparks at one commutator segment and the voltage between brush and commutator segment. This time, we investigated spark generation distribution and their position of the brush, by photographing all the sparks generated during a single-rotation of the motor. As a result, it’s become clear that there is increasing of spark generation in the position near the side where the armature coil of the brush is connected.

B124 高速度カメラによる整流火花発生位置の検討

Using high-speed camera, we have been doing some experiments to clarify the mechanism of the commutation spark generation from the image aspect in universal motor. Previously we mentioned about the cases of single and plural number of sparks generation at single commutator segment This time, we took pictures of all the sparks generated during a single-rotation of the motor and examined sparks generation distribution and their positions of the brush. As a result, we observed that the closer the position to the side where the brush and the armature coil are connected the more sparks are generated. Also we measured the voltage between brush and commutator segment.

The Commutation Spark on a Commutator Segment of Universal Motors

We have been trying to probe the commutation spark mechanism of high-revolving universal motors with two visions of a high-speed camera and brush sparking voltage. The generation of commutation sparks coincides with large pulses in brush sparking voltage, and the sparks occur when the large pulses begin to decrease at the peak. The shape of a single peak value in large pulses becomes a triangle, and plural peak values form square-wave. This paper shows that it is possible to judge generation of commutation sparks easily by observing shapes of peak values of large pulses in armature terminal voltage with a synchroscope.

Photographing the Commutation Spark from Universal Motor by External Laser Trigger Method.

We have attempted to clarify the mechanism of generating commutation spark by means of the images photographed with a high-speed camera. In the photographing system with the high-speed camera, we have contrived a new external laser trigger method that uses a laser beam as trigger signal for shutting of camera. In the external laser trigger method, we provide the motor fan with a 1-mm hole. When the laser beam passes through this hole, a trigger signal is generated, and this trigger signal performs shuttering of the high-speed camera via an optical detector and a pulse generator. The new external laser trigger method has enabled us to photograph spark of any commutator segment of the motor in high-speed rotation. Moreover, it has also become possible to photograph the process from generation to extinction of commutation spark, making us capable of analyzing the commutation spark from photographed images.

A213高速度カメラによる小形モータの整流火花の可視化

Universal motors are used in mainly cleaners. The commutating processes take place by sliding contact of commutator segment and brush, and sparks occur when a segment separates from the brush. The commutation sparks cause wear on the brush and electromagnetic interference to other electronic machines. We visualized images of sparks on high-revolving. motors by a high-speed camera, and analyzed the mechanism of the spark generation. We devised external laser triggering using laser light for shuttering of the camera. This method make it easier to analyze images because it provides with images of the same point of the same segment every time. By photographing spark generation with a high-speed camera by external laser triggering we probed that sparks occurred on every other segment and also visualized that commutation spark occurred on one segment.

Photographing of Commutation Spark by External Laser Triggering.

The single-phase AC commutator motor (universal motor) is a compact, lightweight and high-revolution motor that is widely used in such domestic electric appliances as cleaners, juicers, electric drills. Some problems generated by commutation sparks are wear on the brush and noise impediments. We have therefore attempted to use a high-speed camera to elucidate the commutation spark mechanism visually. We proposed an external trigger method that an argon laser is used for the external trigger signal of high-speed camera. This method enabled us to photograph the motor's commutator segment from any position.

Verification of Commutation Spark Reduction for Brushes of Large DC Motors.

Large DC motors for driving rolling mills should have a compact motor size and tew injurious commutation spark. Good motor performance is got with a no-spark commutation of the brushes. Commutation improvements have been investigated, but problems still remain with commutation leading edge sparking and trailing edge sparking for the progress of running times of the brushes.We developed a new interpole structure to get no sparking on the leading edge. A magnetic flux adjustment winding and a leakage compensation winding is provided adjacent to the radial inner end of the interpole core to improve flux distribution under the interpoles. This approach is effective because leading edge sparking is due to unsymmetrical magnetic flux distribution under the interpoles.Further, we developed a commutation control method to maintain the best conditions on the commutation trailing edge of the brushes. The mothod adjusts the interpole flux according to the commutating conditions.We describe the circuit construction of the commutation control here. Confirmation is made of the reduction effects on the commutation leading and trailing edge sparking of the brushes when using the commutation control system for a 2, 000kW DC motor.

Investigation on spark-numeber by commutation spark measuring apparatus.

Investigation on spark-numeber by commutation spark measuring apparatus.