Zhai Guofu

Dynamic model of particle impact noise detection

The space relay reliability influences the national defence system reliability seriously, and precaution and detection of relay remainder are the pivotal factor to enhance the relay reliability. Particle impact noise detection (PIND) is the American military criterion, but there is a lack of working mechanism research. From the point of view dynamics the paper establishes the collision mathematic models of relay remainder based on PIND, and lots of simulations are completed, and some results are obtained.

Test conditions discussion of particle impact noise detection for space relay

The space relay reliability influences the national defence system reliability seriously, and precaution and detection of relay remainder are the pivotal factor to enhance the relay reliability. Particle impact noise detection (PIND) is the American military criterion, but there is a lack of working mechanism research. From the point of view dynamics the paper establishes the collision mathematic models of relay remainder based on PIND, and studies the remainder motions and collision mechanism, and derives the relations about PIND vibration tables acceleration, frequency, relay cavitys height and recovery coefficient, and lastly gives the corresponding simulations.

Study of a new hybrid switch for the application in the railway

The DC switch is widely used in the railway locomotive system. Electrical arc erosion generated when the switch is operated is the primary factor that affects the life-span of high-power switch, which is harmful to the reliability of the whole system. In this paper, a whole new design method is proposed for the DC 110V/250A hybrid switch which is composed of the power electronic switch, the storage capacitors and the mechanical contactor in parallel. The electrical switch MOSFET is conducted through capturing the signal of the contact voltage when the mechanical switch is making to eliminate the bouncing electrical arc of the contactor. And the capacitors are used to absorb the energy of arc generated when the contractor is breaking. This paper presents a method to extract the parasite parameters and makes optimum design for the hybrid switch. The experiment results show that the influence of arc is mostly eliminated when the hybrid switch is operated so that the reliability and electrical life-span of the switch are enhanced. The new design method of the hybrid switch is quite different from the traditional design idea and makes it possible for the hybrid switch to be utilized in high power situation more extensively, which shows a good market prospect. The new hybrid switch has been used in the railway system and has a good effect.

New method of tolerance design of electromagnetic relay reliability

Reliability design is a very important phase of reliability engineering. In this paper, a new method of tolerance design of electromagnetic relay reliability, which is based on the design of system optimization and parameter optimization, is presented. This method seeks the optimal cooperation between the tolerance of the electromagnetic attractive force characteristic and that of the spring force characteristic under given reliability indexes for pick-up and drop-out by adjusting the design variables and the tolerance. This method enhances the controllability of product design quality, makes perfect consistency of output characteristic, and assures the inherent reliability and the certified rate of products.

Rail flaw detection system based on electromagnetic acoustic technique

As a result of the development of higher speeds and heavier loads of rail networks, rail defects have been more serious than ever before. Current piezoelectric ultrasonic detection devices are often inadequate for rail inspection, due to high misjudgement or undetected error rate, and complex structure. This paper introduces a novel rail detection system. The system is based on multi-channel electromagnetic acoustic transducers under the control of DSP. Cumulative average and cross-correlation algorithms are realized by FPGA, exploiting the advantages of FPGA in high calculating speed and designing flexibility. Combining EMATs with FPGA, the system is free of couplant, compact in structure and low use-cost, and can realize an overall detection of rails.

Research on the analytical method of contact vibration performance of reed relay

Inherent frequency and vibration limited acceleration are the two major parameters that determine the performance of reed relay contacts under a mechanical environment. Based on the theory of materials mechanics and vibration mechanics, a mathematical model of the reeds vibration mode is presented in this paper. By using a classical analytic approach and finite element method, the failure criterion of a reed relay in vibration is given; the vibration mode of the reed system is analyzed and the transient process of the displacement of the reed contact is simulated. The vibration performance of a reed contact under the conditions of sinusoidal actuating vibration with high frequency is provided and analyzed. A discussion of the effect of reed contact dimensional parameters on inherent frequency and vibration performance is emphasized.

Permanent-Magnet Equivalent Model of Calculating Relay's Static Attractive Torque Characteristics by Finite Element Method

The permanent magnet (PM) is the key part of the relay. This paper aims to solve the problem of the uneven magnetization for the PM with nonlinear demagnetization curve after magnetizing and demagnetizing. A method partitioning the PM along the magnetization direction and the vertical direction of magnetization according to the condition of the specific magnetization of the PM was presented. By this method, the demagnetization model of the PM was built, the state of the PM magnetization was simulated under the demagnetizing magnetic intensity, and the recoil line and its initial point of each partition of the PM were obtained. Then the characteristic of the recoil line of each partition was used as its magnetic characteristic for the equivalent model of the PM to calculate the static torque characteristics under the demagnetizing magnetic field. Finally, the static torque characteristics of simulation and experiment were compared and the validity of the equivalent model presented was verified.

The Effect of Coil on Combined Three-Subsection Permanent Magnet in Close Magnetic Circuit Model

Working characteristic of the permanent magnet (PM) is a key point of PM relays design. Soft magnetic material and coil will effect the working characteristic of PM. In order to analyze the effect of coil, a combined three-subsection PM in close magnetic circuit model (CTPMC) is built based on the equivalent magnetic circuit, and its theoretical model is established under the magnetic potential effect. Through the theoretical deduction, it is concluded that each PM subsection works at different recoil lines and the working points would change due to the effect of coil. Finally, the above theoretical analysis results are validated by simulation and experiments.

Thermal analysis of hermetically sealed electromagnetic relay in high and low temperature condition

Hermetically sealed structure is the optimal style to protect electromagnetic relay (EMR) from formidable working environment. Each product shall be subjected to thermal environment shock in accordance with MIL-STD-202 from -65degC to +125degC temperature, so it is of great importance for thermal analysis of EMR to increase the thermal stability and reliability requirement. In this paper, special finite element analysis (FEM) software ANSYS, was used for the accurate simulation of the internal relay structure. The elevated temperature characteristic of relay is investigated considering comprehensive thermal conductivity and convection effect. Internal complex heat transfer paths of EMR are determined and the influence of different temperature condition of inert gas on thermal performance is also researched. The results of the analysis can be useful for reliability thermal design of hermetically sealed EMR.

Research and application of testing and analyzing system for sealed relay's time parameters

The contacts mechanical parameters of sealed relay (such as contact over travel and contact force etc.) cannot be measured after the relay has been assembled. However, the time parameters of contact can be measured and can qualitatively reflect the change of contact mechanical parameters, which directly influence the reliability of contact. Hence, the time parameters can be used to qualitatively describe the reliability of contact. The testing and analyzing equipment for time parameters of sealed relays contact was designed which took industrial control computer as central processor. By using the A/D data acquisition card specially designed (including ten sample channels, 4 MHz sample rate, 64 K byte data per channel stored), the current of single coil or double coils and the voltage of eight sets of change-over contacts could be sampled at the same time. Time parameters which would influence the contacting reliability, such as the over travel time, change-over time, bounce time and arc duration could be tested synthetically by dealing with the digital signal of coil current and contact voltage. The arc duration and the breaking over travel time of some type relay were tested by this system and their rules were analyzed.