hanjian_canuck
加入时间: 2004/11/22
文章: 17
经验值: 69
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作者：hanjian_canuck 在 罕见奇谈 发贴, 来自 http://www.hjclub.org
您这人真够懒,稍微翻翻电工原理几分钟的事也不愿做,老芦说的用电容器是全世界世界通行的功率因数补偿手段,下面是关于功率因数的解释.
An electrical load that operates on alternating current requires apparent power, which consists of real power plus reactive power. Real power is the power actually consumed by the load. Reactive power is repeatedly demanded by the load and returned to the power source, and it is the cyclical effect that occurs when alternating current passes through a load that contains a reactive component. The presence of reactive power causes the real power to be less than the apparent power, and so, the electric load has a power factor of less than 1.
The reactive power increases the current flowing between the power source and the load, which increases the power losses through transmission and distribution lines. This results in operational and financial losses for power companies. Therefore, power companies require their customers, especially those with large loads, to maintain their power factors above a specified amount (usually 0.90 or higher) or be subject to additional charges. Electrical engineers involved with the generation, transmission, distribution and consumption of electrical power have an interest in the power factor of loads because power factors affect efficiencies and costs for both the electrical power industry and the consumers. In addition to the increased operating costs, reactive power can require the use of wiring, switches, circuit breakers, transformers and transmission lines with higher current capacities.
Power factor correction attempts to adjust the power factor of an AC load or an AC power transmission system to unity (1.00) through various methods. Simple methods include switching in or out banks of capacitors or inductors which act to cancel the inductive or capacitive effects of the load, respectively. For example, the inductive effect of motor loads may be offset by locally connected capacitors. It is also possible to effect power factor correction with an unloaded synchronous motor connected across the supply. The power factor of the motor is varied by adjusting the field excitation and can be made to behave like a capacitor when over excited.
你讲的电动机启动瞬峰电流问题与功率因数风马牛不相及. 功率因数问题源于负载的非纯阻性所导致的负载电压与电流相位差, 它导致的结果是输电系统的损耗增加和对电网负载能力的浪费, 它基本上是个稳态过程. 而电动机启动瞬峰是由于电动机转子的机械惯性所致, 笼统讲,绝大多数交流感应电动机都是设计工作在额定转速, 输出扭矩取决于旋转磁场的转速与转子转速之差, 这个差值越大, 输出扭矩就越高, 电流消耗也越高. 在通电启动瞬间, 转子是静止状态, 而旋转磁场的转速因为是由电源频率决定, 是个定数, 所以此时两者具有最大转速差, 所以会在瞬间消耗比正常稳定工作时高很多的电流,用于加速电机转子(及负载). 顾名思义, 电流瞬峰只发生在电机启动的瞬间. 电机功率越大, 转子相应就越重, 这个问题就越严重.
很显然,这两个问题的来源,作用原理,解决办法都不同,不明白你为何说它们是一回事.
作者：hanjian_canuck 在 罕见奇谈 发贴, 来自 http://www.hjclub.org |
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谢谢河边网友，向芦笛道歉
