电磁铁是一个带有铁心的通电螺线管，电磁铁的磁性大小与通电电流与螺线管的匝数有关。磁铁工作原理： 电磁铁的工作原理就是采用电磁感应原理，主要运用毕奥-沙瓦定律与基尔霍夫定律进行磁场设计、计算。
电磁铁的特点是：电磁铁本身有无磁性， 可以通过通断电流来控制，磁性的大小可以改变电流的大小来控制，磁极的方向有电流的方向决定。
电磁铁应用范围
各类小型精密电磁铁及电磁铁应用组件，作为自动控制系统的执行器件，已被广泛应用于工业自动化控制、办公自动化、医疗器械等各个领域。如办公设备、影像器材、银行设备、包装机械、医疗器械、食品机械、纺织机械、自动分拣机、自动柜员机、自动售货机、卡片打孔器、电磁锁、各种遥控装置、制动装置、计数装置、门禁系统等。
电磁铁选型主要参数
客户选用或定做所需的电磁铁需要考虑以下的技术参数：
1 外形：安装电磁铁位置所能容纳的最大尺寸：长；宽；高，
2 电磁铁的最大行程及其吸力要求，断电后的复位力要求
3 提供给电磁铁的电源最大电压；电流？电压稳定性，交流/直流供电，能否提供正；负脉冲电源？
4电磁铁是否需要长期不间断工作；断续工作，每次最长的通电时间及两次通电之间最短的间歇；
5 电磁铁的用途，使用电磁铁的环境特殊要求，如温度; 湿度; 冲击; 振动; 加速度等
电磁铁的分类方法
1．按动作方式：
保持式 如电磁离合器、电磁卡盘、起重电磁铁等
吸引式 各种自动电器继电器、接触器、电磁阀门、电动锤、电铃等
2． 照激磁线圈供电的种类： 直流、交流
3．按照动作速度：快速动作、正常动作、延缓动作
4. 按衔铁的运动方式：直动式、转动式
5. 按磁路的形状： 开路导磁体如螺管式；闭路导磁体如盘式（起重电磁铁）、拍合式、Ⅱ型、Ⅲ型（及E型）、装甲螺管式
注： 一般在工业上根据结构，可以简单的合并为三大类型：
拍合式： 盘式、Ⅱ型从原理上可归到此类，该类行程最短
螺管式： 行程最长
E 型： 行程介于上两者之间
DC solenoids, hydraulic solenoid valve, solenoid water valve, solenoid pump
The followings are the relationship between force and resistance, current, and voltage. The power is related to the size of wire and the number of windings wire produces stroke.
The shorter the stroke is the bigger the force is. When inquiring force, you must mention the stroke, because they are directly relevant.
Normally, the stronger the power the greater the force is. Both of them have direct ratio. But, when power reaches a certain level that solenoid approaches magnetic saturation, the force increase little.
If the resistance, current and voltage vary while the power and coil remain the same. The force remains.
a. If the coil resistance is kept unchanged when increasing the number of windings with bigger size wire, the force will increase. If the original coil is already fully wound, the enameled wire can't be changed, otherwise, the coil will be too bigger to fit into the iron shell.
b. Increasing the number of windings with the same size enameled wire only results in decreased force, because the negative effect on the force of the resistance increase outweighs the positive effect of the increase of the winding number.
c. Changing the enameled wire size (the resistance being changed) but keeping the power (P= U2/R£»R¡¢U being unchanged, but keeping P), we will get unchanged force.
Operation time determines power, that is, if the operation time continues a long period of time, the power can't be set too big, otherwise, solenoid will be damaged by overheating.
If you slect SDO-0837L model solenoid, requiring a stroke of 5mm, 500-g force, not mentioning size and power, we may offer SOD-0837L already in storage in stead of winding for a new solenoid, so as for a quick sample delivery, for instance, selecting the solenoid of 36 ohm.
After the customer has received the product, they power it with regulated power supply, and adjust the voltage (stroke set at 5mm). The force will increase with the voltage increase, and the solenoid will heat up increasingly apparently. When the force reaches 500g, the voltage is 24V. This means that SDO-0837L is able to produce a force of 500g when power is set 16W(242/36=16), stroke 5mm.
If you use 12V power supply, the resistance will be changed to 9 ohm in order to reach the same force while keeping the 16W power (R=U2/W=122/16=9). For 16W power, the solenoid produces more heat than permited. Or the limited temperature rises value(usually ambient temperature +65° or the current exceeds that customer permits, a bigger sized solenoid shall be selected to avoid that overheating.
The adoption of above methods will reduce the number of sample delivery due to resistance changes.
For high sample success rate, customers are kindly required the following conditions for solenoid use.
Maximum stroke, force requirement, voltage (or current and resistance), expected life (total operation times within operational life), application purpose (for what equipment), and other information that can be offered
