Mike Krzyzewski is really a famous coach of Dream Team. She has coached north america men's basketball team for some time, that's clinched numerous medals for his country. Following London Olympic was over, Krzyzewski told The Associated Press that this game will be his final one as national coach, a job he's held for seven years. He had left open the possibility of staying with the team beyond the London Games, when practice on Saturday said these will be his last Olympics.When asked if he was sure, Krzyzewski didn't hesitate before again saying, "yes," this will be his last game "If we could win it, then it might be three major championships in a row, i always do not know when that has been done because we haven't usually won the globe championships," Krzyzewski said. "It becomes an enormous thing for the program." Whatever, he's an awesome coach. His achievement are going to be remembered by the country.

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软启动器如何实现轻载节能

2014/8/18 9:01:50点击:

目前,交流感应电动机以其低成本、高可靠性和少维护等优点5,在各种工业领域中得到广泛应用。但是,它在直接起动时,存在着两个缺点:首先,它的起动电流可高达额定电流的5~7倍,这就要求电网裕量比较大,而且降低电气控制设备的使用寿命,增加维护成本。
其次,起动转矩可达正常转矩的两倍,这会对负载产生冲击,增加传动部件的磨损和额外的维护。基于以上原因,产生了交流应电动机降压起动设备。
传统减压起动方法有Y/△起动和自耦变压器降压两种,每种都有各自的特点。电动机用Y/△起动时,在切换瞬间会出现很高的电流尖峰,会产生破坏性的动态转矩,其引起的机械振动对电动机转子、齿轮以及负载等都是非常有害的。自耦变压器降压起动设备体积庞大,成本高,而且还存在与负载匹配的电动机转矩难控制等缺点。

笼型异步电机是感性负载,在运行中,定子线圈绕组中的电流滞后于电压。如电机工作电压不变,处于轻载时,功率因数低,处于重载时,功率因数高。软起动器能实现在轻载时,通过降低电机端电压,提高功率因数,减少电机的铜耗、铁耗,达到轻载节能的目的;负载重时,则提高电机端电压,确保电机正常运行。

 

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