Maxwell Bridge, Types, Advantages & Disadvantages
Table of Contents
Maxwell bridge is the name of the bridge that is used to measure the circuit’s self-inductance. The Wheatstone Bridge has evolved into this form. According to the comparison principle, which the Maxwell bridge operates on, the value of an unknown inductance is ascertained by contrasting it with a known value or a standard value.
Types of Maxwell’s Bridge
To calculate the circuit’s self-inductance, two techniques are used. Those are
- Maxwell’s Inductance Bridge
- Maxwell’s inductance Capacitance Bridge
Maxwell’s Inductance Bridge
By comparing it to the known value of the typical self-inductance in such bridges, it is possible to estimate the value of the unknown resistance. So The figure below displays the balance Maxwell bridge’s connection diagram.
Let, L1 – unknown inductance of resistance R1.
L2 – Variable inductance of fixed resistance r1.
R2 – variable resistance connected in series with inductor L2.
R3, R4 – known non-inductance resistance
At balance,
So With the aid of the resistance box, the R3 and R4 resistance values range from 10 to 1000 ohms. Occasionally, additional resistance is also added to the circuit to balance the bridge.
The phasor diagram of Maxwell’s inductance bridge is shown in the figure below.
Maxwell’s Inductance Capacitance Bridge
With the aid of the standard variable capacitance, the unknown resistance in this type of bridge is measured. The figure below shows the Maxwell Bridge’s connection diagram.
Let, L1 – unknown inductance of resistance R1.
R1 – Variable inductance of fixed resistance r1.
R2, R3, R4 – variable resistance connected in series with inductor L2.
C4 – known non-inductance resistance
For balance condition,
So By separating the real and imaginary equation we get,
So The aforementioned equation demonstrates that the variables R4 and C4 for bridges are present in only one of the two equations, proving that both equations are independent.
The circuit quality factor is expressed as
Phasor diagram of Maxwell’s inductance capacitance bridge is shown in the figure below.
Advantages
The following are the advantages of the Maxwell bridges
- The circuit’s balance equation is frequency-free.
- The two balance equations operate separately from one another.
- So The high range inductance is measured using the Maxwell’s inductor capacitance bridge.
Disadvantages
So The main disadvantages of the bridges are
- A very costly variable capacitor is needed for the Maxwell inductor capacitance bridge. As a result, the standard variable capacitor is occasionally used in bridges.
- So Only medium quality coils are measured using the bridge.
The advanced version of the Maxwell’s Bridge, the Hays Bridge, is used to measure circuit inductance due to the following drawbacks.