具有滑动液体-金属接触的可行单极发电机

参数共振驱动的单极圆盘发电机

Homopolar oscillating-disc dynamo driven by parametric resonance

我们使用一个简单的模型，Bullard型磁盘发电机，其中磁盘的转速受到谐波振荡，分析产生的磁场的参数共振机制。这个问题是由阻尼Mathieu方程。定义磁场增长率的Floquet指数根据振荡的振幅和频率计算。首先，我们表明，发电机可以激发在显着亚临界光盘转速时，后者受到一定频率的谐波振荡。其次，在超临界平均转速，发电机也可以被抑制，但只有在窄频带和足够大的振荡幅度。

A homopolar disc dynamo experiment with liquid metal contacts

We present experimental results of a homopolar disc dynamo constructed at CICATA-Querétaro in Mexico. The device consists of a flat, multi-arm spiral coil which is placed above a fast-spinning metal disc and connected to the latter by sliding liquid-metal electrical contacts. Theoretically, self-excitation of the magnetic field is expected at the critical magnetic Reynolds number Rm~45, which corresponds to a critical rotation rate of about 10 Hz. We measured the magnetic field above the disc and the voltage drop on the coil for the rotation rate up to 14 Hz, at which the liquid metal started …

Dynamo action in sliding plates of anisotropic electrical conductivity

With materials of anisotropic electrical conductivity, it is possible to generate a dynamo with a simple velocity field, of the type precluded by Cowling's theorems with isotropic materials. Following a previous study by Ruderman and Ruzmaikin [1] who considered the dynamo effect induced by a uniform shear flow, we determine the conditions for the dynamo threshold when a solid plate is sliding over another one, both with anisotropic electrical conductivity. We obtain numerical solutions for a general class of anisotropy and obtain the conditions for the lowest magnetic Reynolds number, using a…

Realization of Bullard's disc dynamo

We report experimental results from three successful runs of a Bullard-type homopolar disc dynamo. The set-up consisted of a copper disc with a radius of 30 cm and thickness of 3 cm which was placed co-axially beneath a flat, multi-arm spiral coil of the same size and connected to it electrically at the centre and along the circumference by sliding liquid-metal contacts. The magnetic field was measured using Hall probes which were fixed on the top face of the coil. We measured also the radial voltage drop across the coil. When the disc rotation rate reached $Ω\approx 7$ Hz, the magnetic field …