|
Superconducting electric machines are electromechanical systems that rely on the use of one or more superconducting elements. Since superconductors have no DC resistance, they typically have greater efficiency. The most important parameter that is of utmost interest in superconducting machine is the generation of a very high magnetic field that is not possible in a conventional machine. This leads to a substantial decrease in the motor volume; which means a great increase in the power density. However, since superconductors only have zero resistance under a certain superconducting transition temperature, ''Tc'' that is hundreds of degrees lower than room temperature, cryogenics are required. Now there is more interest in superconducting AC synchronous electric machines (alternators and synchronous motors). The direct current electromagnet field winding on the rotor (rotating member) use superconductors but the alternating current multiphase winding set on the stator (stationary members), which have no practical support by superconductors, uses conventional, normal conduction copper conductors. Often the stator conductors are cooled to reduce, but not eliminate, their resistive losses. ==History== DC homopolar machines are among the oldest electric machines. Michael Faraday made one in 1831. Superconducting DC homopolar machines use superconductors in their stationary field windings and normal conductors in their rotating pickup winding. In 2005 the General Atomics company received a contract for the creation of a large low speed superconducting homopolar motor for ship propulsion. Superconducting homopolar generators have been considered as pulsed power sources for laser weapon systems. However, homopolar machines have not been practical for most applications. In the past, experimental AC synchronous superconducting machines were made with rotors using low-temperature metal superconductors that exhibit superconductivity when cooled with liquid helium. These worked, however the high cost of liquid helium cooling made them too expensive for most applications. More recently AC synchronous superconducting machines have been made with ceramic rotor conductors that exhibit high-temperature superconductivity. These have liquid nitrogen cooled ceramic superconductors in their rotors. The ceramic superconductors are also called high-temperature or liquid-nitrogen-temperature superconductors. Because liquid nitrogen is relatively inexpensive and easy to handle, there is a greater interest in the ceramic superconductor machines than the liquid helium cooled metal superconductor machines. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Superconducting electric machine」の詳細全文を読む スポンサード リンク
|