{"status":"1","message":"\u6210\u529f","data":{"detail":{"id":28,"title":"Fundamentals of AC Bridge","keywords":"AC bridge\r\nSchering bridge,\r\nMaxwell bridges, Hay bridge,\r\nWheatstone bridge\r\nThe balance condition of AC Bridges \r\n","description":"","image":"https:\/\/apt-image.oss-accelerate.aliyuncs.com\/f2e095e5446111aa4d5f6f59cc7901c7.jpg","category_id_1":37,"content":"

1.AC Bridge <\/span><\/p>

\"\u672a\u6807\u9898-1.jpg\"\/<\/p>

Figure 1 AC Bridge Principle<\/span><\/p>

AC bridges consist of 4 pieces of AC electrical components,Z1,Z2,Z3,and Z4. They may be resistor, inductor and capacitor. One zero indicator G, it is used to check if the bridge in balance condition ,ie, I0=0. AC voltage is applied between terminals a and b.<\/span><\/p>

 2.The balance condition of AC Bridges  <\/span><\/p>

While one sinusoidal AC voltage is applied between terminals a and b, then the balance condition of AC Bridge as below:<\/span><\/p>

\"\u672a\u6807\u9898-2.jpg\"\/<\/span><\/p>

Both conditions above formulas must be met at the same time. i.e.<\/span><\/p>

Z1Z3 amplitude product= the product of Z2 and Z4;<\/span><\/p>

\u03c61 is the phase angle of Z1, So do \u03c63, \u03c62,and \u03c64. The sum of\u03c61 and \u03c63, must be equal to the sum of\u03c62,and \u03c64. <\/span><\/p>

3.Commonly used AC Bridges<\/span><\/p>

3.1 Schering Bridge, also called Capacitance Bridge <\/span><\/strong><\/p>

Actual capacitor doesn\u2019t pure capacitance, It has dielectric loss.<\/span><\/p>

One actual capacitor could be equal to one pure capacitor and one resistor in serial or in parallel.<\/span><\/p>

3.1.1 In serial for low dielectric loss bridge <\/span><\/strong><\/p>

\"\u672a\u6807\u9898-3.jpg\"\/<\/p>

Figure 2. Schering Bridge-Rx in serial <\/span><\/p>

The balance condition of AC Bridge as below:<\/span><\/p>

\"\u672a\u6807\u9898-4.jpg\"\/<\/p>

Both conditions above formulas must be met at the same time<\/span><\/p>

tg\u03b4=\u03c9CxRx=\u03c9CnRn<\/span><\/p>

3.1.2 In parallel for big dielectric loss bridge<\/span><\/strong><\/p>

\"\u672a\u6807\u9898-5.jpg\"\/<\/p>

Figure 3. Schering Bridge-R\u2019x in parallel<\/span><\/p>

The balance condition of AC Bridge as below:<\/span><\/p>

\"\u672a\u6807\u9898-6.jpg\"<\/p>

3.2 Inductance Bridge <\/span><\/strong><\/p>

Inductance Bridge is used to measure unknown inductance. Usually, standard capacitor is used as the criterion to measure unknown inductor.<\/span><\/p>

Actual inductor doesn\u2019t pure inductance, It has resistance.<\/span><\/p>

XL\/R.is called Q vale of one inductor. XL=\u03c9L<\/span><\/p>

3.2.1 Maxwell Bridge which is used to measure low Q value inductor<\/span><\/strong><\/p>

\"\u672a\u6807\u9898-7.jpg\"\/<\/p>

Figure 4. Maxwell Bridge<\/span><\/p>

\"\u672a\u6807\u9898-8.jpg\"\/<\/span><\/p>

<\/span><\/p>

For Maxwell Bridge, its balance is independent of its AC power frequency.<\/span><\/p>

3.2.2 Hay Bridge which is used to measure big Q value inductor<\/span><\/strong><\/p>

\"\u672a\u6807\u98989.jpg\"\/<\/span><\/p>

Figure 5. Hay Bridge<\/span><\/p>

\"\u672a\u6807\u989810.jpg\"\/<\/span><\/p>

3.3 Wheatstone bridge to measure unknown resistances.<\/strong><\/span><\/p>

\"\u672a\u6807\u9898-11.jpg\"\/<\/strong><\/span><\/p>

<\/p>

Figure 6. Wheatstone Bridge<\/span><\/p>

<\/p>

\"\u672a\u6807\u9898-12.jpg\"\/<\/p>

To measure unknown resistance, Usually AC bridge is replaced with DC bridge.<\/span><\/p>

Related Documents :<\/span><\/p>

SCHERING & MAXWELL BRIDGES FOR STUDENT PRACTICE MODEL UB4858<\/a><\/span><\/p>

HIGH VOLTAGE SCHERING BRIDGE MODEL QS35A<\/a><\/span><\/p>

<\/span><\/p>

<\/strong><\/span><\/p>","pdf_1":"https:\/\/apt-image.oss-accelerate.aliyuncs.com\/Fundamentals%20of%20AC%20Bridge.pdf","ytb_video":"","introduction":"","thumbnail":"","sort":0,"create_time":"2023-06-14 10:55:02"},"recommend_products":[{"id":182,"products_image1":"https:\/\/apt-image.oss-accelerate.aliyuncs.com\/Transformer%20Applied%20Voltage%20Test%20Systems-500.gif","products_title":"Transformer Applied Voltage Test Systems"}],"comment":[]}}