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Helical coil electromagnetic launchers (HEMLs) using brush-commutation strategy, solving the problem of synchronization control perfectly, have a promising prospect in accelerating big mass to high speed. One of its current technical bottlenecks is the arc erosion caused by the brush commutation, which damages the current-fed rails, besides reduces the energy conversion efficiency of HEMLs. During the commutation process, the leading, trailing edges of the commutating brush act as the closing, opening switches, respectively. When the brush-controlled circuit turns ON and OFF, the commutation-induced voltage (CIV) is a key to research the arc erosion of brushes. It can be concluded that the CIV is proportional to the current, the commutation inductance gradient (CIG), and the projectile velocity by a theoretical analysis and numerical simulation. The CIG is a critical structural parameter of HEMLs, and the formulas of the CIG for single and multiple turn commutation are deduced. Compared with single turn commutation, the current in the commutating turns changes moderately, and the CIV is lower in the case of multiple turn commutation. Two armatures of 35 turns and 135 turns were tested in an HEML of coil-unit barrel; the experimental results are in good agreement with the theoretical calculations. [ABSTRACT FROM AUTHOR]

Helical coil electromagnetic launchers (HEMLs) using rail-fed strategy, local excitation and single-turn commutation, solve the problem of synchronization control perfectly. Through the simulation, a novel helical coil launcher is designed using the basic HEML's structure. A D-shaped cross section armature is proposed to achieve the maximum projectile velocity. The energizing length of the driving coil, as well as, the armature position of the maximum force is determined. The maximum driving force on the armature increases with the increasing coil axial length and the armature acceleration reaches its maximum value when the ratio of axial to radial length of the coil is 1:2. The force distribution of the armature and driving coils is analyzed. [ABSTRACT FROM PUBLISHER]

As a kind of future weapon, an electric launcher uses high current to drive projectiles reaching velocities on the order of several kilometers per second. As is known, high and rapidly changing currents through electric launcher can lead to strong radiation. A PSPICE model is used to analyze the frequency content of currents in the helical electromagnetic launcher (HEML) by nonuniform fast Fourier transform. The frequency spectrum is mainly determined by conducting duration and intensity of entering current. The main frequency of HEML is low, but high-frequency components can produce more radiation. The total radiation can be considerable. [ABSTRACT FROM PUBLISHER]

A model is developed to investigate the commutation process of a helical coil electromagnetic launcher (HCEML) structure. When the armature moves, the motion of the projectile coils’ magnetic energy would supply reactive power to move the leakage into and out of the coil windings of the launcher to accomplish the commutation. The energy conversion of the coil electromagnetic launcher can be considered as the process of energy transfer from the back commutation coils to the excited coils and then from the excited turns to the front commutation coils. In this paper, governing equations of the commutation were deduced theoretically, and finite-element model of HCEML was established in ANSOFT MAXWELL. Then a deeper circuit investigation into the overall performance of commutation was carried out by means of PSPICE software. The validity of the theoretical analysis and that of the circuit network model were finally verified by experiments. The results show that during the commutation process, the current of back commutation coils drops to zero with no energy remaining in the internal; the current of front commutation coils and drive–projectile coil system gradually changes to a stable value, which is related to the geometric parameters of the launcher; the drive–projectile coil system releases energy overall that is mainly used to increase the kinetic energy of the projectile; the power supply system has little effect on energy conversion and transformation at the commutating moment and just keeps the voltage and current from decaying due to the impedance and inductance of the launcher system. [ABSTRACT FROM PUBLISHER]