Transformatorê Diferansiyel Variable Lineer LVDT

LVDT-yn Pêşnûs

Terma LVDT li gorî Linear Variable Differential Transformer dike. Ev ê inductive transducer yekêm e ku bi serkeftin bikiyê ji linear motion hatine têr kirin bia electrical signal.

Output di secondary de ya vê transformer-ê differential e, lê bina ev dike. Ev inductive transducer yekêm e ku hêzandî yên din a jîra inductive transducers yên din dike.

LVDT-yn Binafesazî

Taybetmendiyên Sernavê Binafesazî

• Transformera werin primary winding P û du secondary windings S1 û S2 piştî cylindrical former (ku li navbera çarçovek û core ye).

• Herdû secondary windings an da nûmera pêkhatan ve tevahî ne, û wan di her du pêşka primary winding de ne.

• Primary winding bi AC source girdekirin ku flux di air gap de dê bike û voltages di secondary windings de dê induc bikin.

• Movable soft iron core di navbera former de girdekirin û displacement ku mideya mideye bi iron core girdekirin.

• Iron core li goralî high permeability e ku ji bo reducing harmonics û high sensitivity ya LVDT yardim dike.

• LVDT di stainless steel housing de girdekirin ji bo electrostatic û electromagnetic shielding.

• Her du secondary windings bi şêwek werin connect kirin ku output resulted difference between the voltages of two windings be.

Principela Vejirî û Karkeşanî

Çi primary bi AC source girdekirin, alternating current û voltages di secondary de ya LVDT hatine têr kirin. Output di secondary S1 de e1 û di secondary S2 de e2. Naha, differential output,

Ev equation explains the principle of Operation of LVDT.

Naha, sê cases according to the locations of core which explains the working of LVDT are discussed below as,

• CASE I When the core is at null position (for no displacement)
  When the core is at null position then the flux linking with both the secondary windings is equal so the induced emf is equal in both the windings. So for no displacement the value of output eout is zero as e1 and e2 both are equal. So it shows that no displacement took place.

• CASE II When the core is moved to upward of null position (For displacement to the upward of reference point)
  In the this case the flux linking with secondary winding S1 is more as compared to flux linking with S2. Due to this e1 will be more as that of e2. Due to this output voltage eout is positive.

• CASE III When the core is moved to downward of Null position (for displacement to the downward of the reference point). In this case magnitude of e2 will be more as that of e1. Due to this output eout will be negative and shows the output to downward of the reference point.

Output VS Core Displacement A linear curve shows that output voltage varies linearly with displacement of core.

Some important points about magnitude and sign of voltage induced in LVDT

• The amount of change in voltage either negative or positive is proportional to the amount of movement of core and indicates amount of linear motion.

• By noting the output voltage increasing or decreasing the direction of motion can be determined

• The output voltage of an LVDT is linear function of core displacement .

Advantages of LVDT

• High Range – The LVDTs have a very high range for measurement of displacement.they can used for measurement of displacements ranging from 1.25 mm to 250 mm

• No Frictional Losses – As the core moves inside a hollow former so there is no loss of displacement input as frictional loss so it makes LVDT as very accurate device.

• High Input and High Sensitivity – The output of LVDT is so high that it doesn’t need any amplification. The transducer posseses a high sensitivity which is typically about 40V/mm.

• Low Hysteresis – LVDTs show a low hysteresis and hence repeatability is excellent under all conditions

• Low Power Consumption – The power is about 1W which is very as compared to other transducers.

• Direct Conversion to Electrical Signals – They convert the linear displacement to electrical voltage which are easy to process

Disadvantages of LVDT

• LVDT is sensitive to stray magnetic fields so it always requires a setup to protect them from stray magnetic fields.

• LVDT gets affected by vibrations and temperature.

It is concluded that they are advantageous as compared than any other inductive transducer.

Applications of LVDT

1. We use LVDT in the applications where displacements to be measured are ranging from a fraction of mm to few cms. The LVDT acting as a primary transducer converts the displacement to electrical signal directly.

2. The LVDT can also act as a secondary transducer. E.g. the Bourbon tube which acts as a primary transducer and it converts