DQZHAN技術訊：電磁鐵基本知識
電磁鐵是一個帶有鐵心的通電螺線管，電磁鐵的磁性大小與通電電流與螺線管的匝數有關。磁鐵工作原理： 電磁鐵的工作原理就是采用電磁感應原理，主要運用畢奧-沙瓦定律與基爾霍夫定律進行磁場設計、計算。
電磁鐵的特點是：電磁鐵本身有無磁性， 可以通過通斷電流來控制，磁性的大小可以改變電流的大小來控制，磁極的方向有電流的方向決定。
電磁鐵應用范圍
各類小型精密電磁鐵及電磁鐵應用組件，作為自動控制系統的執行器件，已被廣泛應用于工業自動化控制、辦公自動化、醫療器械等各個領域。如辦公設備、影像器材、銀行設備、包裝機械、醫療器械、食品機械、紡織機械、自動分揀機、自動柜員機、自動售貨機、卡片打孔器、電磁鎖、各種遙控裝置、制動裝置、計數裝置、門禁系統等。
電磁鐵選型主要參數
客戶選用或定做所需的電磁鐵需要考慮以下的技術參數：
1 外形：安裝電磁鐵位置所能容納的*大尺寸：長；寬；高，
2 電磁鐵的*大行程及其吸力要求，斷電后的復位力要求
3 提供給電磁鐵的電源*大電壓；電流？電壓穩定性，交流/直流供電，能否提供正；負脈沖電源？
4電磁鐵是否需要長期不間斷工作；斷續工作，每次*長的通電時間及兩次通電之間*短的間歇；
5 電磁鐵的用途，使用電磁鐵的環境特殊要求，如溫度; 濕度; 沖擊; 振動; 加速度等
電磁鐵的分類方法
1．按動作方式：
保持式 如電磁離合器、電**盤、起重電磁鐵等
吸引式 各種自動電器繼電器、接觸器、電磁閥門、電動錘、電鈴等
2． 照激磁線圈供電的種類： 直流、交流
3．按照動作速度：快速動作、正常動作、延緩動作
4. 按銜鐵的運動方式：直動式、轉動式
5. 按磁路的形狀： 開路導磁體如螺管式；閉路導磁體如盤式（起重電磁鐵）、拍合式、Ⅱ型、Ⅲ型（及E型）、裝甲螺管式
注： 一般在工業上根據結構，可以簡單的合并為三大類型：
拍合式： 盤式、Ⅱ型從原理上可歸到此類，該類行程*短
螺管式： 行程*長
E 型： 行程介于上兩者之間
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
