In modern thermal power plants, the precise control of turbine throttle valves is directly related to the efficiency and safety of the unit. As the core sensing element of this system, the LTM-6A-I LVDT transmitter is like a precise central nervous system, converting mechanical displacement into highly reliable control instructions. This system realizes the transformation from micron-level displacement to industrial control signals through the perfect combination of electromagnetic induction principle and intelligent signal processing technology.

I. Working principle of LVDT: the art of electromagnetic induction

The signal conditioning unit of the LVDT transmitter LTM-6A-I adopts a conditioning circuit built with AD598 dedicated chip, including: oscillator module and synchronous demodulator, generating a stable excitation signal of 3Vrms/3kHz to eliminate the measurement error caused by phase offset.

Built-in 16-bit ADC and DSP processor realize nonlinear correction, dynamic filtering with adjustable cutoff frequency of 10-500Hz, and dual-channel redundant verification function.

II. Decryption of the whole process of signal conversion

We all know that the core of LVDT is composed of two or three groups of precision coils, and the iron core slides freely in the skeleton. This symmetrical structure makes the induced electromotive force generated by S1/S2 completely offset when the core is in the center position, and the output is the zero point reference. When 1-10kHz AC is passed into the primary coil, the displacement of the core will break the electromagnetic balance of the secondary coil. Every 0.01mm displacement will produce a voltage difference of about 2mV, and the linearity error is less than ±0.25%. This non-contact measurement avoids mechanical wear and has a theoretical life of up to 5 million reciprocating movements.

The process of displacement-electrical signal conversion starts with electromagnetic coupling. The movement of the core causes the mutual inductance of the secondary coil to change, generating an AC voltage proportional to the displacement. Within the ±25mm range, the original signal amplitude can reach ±10V. The LVDT transmitter LTM-6A-I uses phase-sensitive detection technology to convert AC signals into DC, with an adjustable gain range of 40-60dB and a noise suppression ratio of >80dB.

The standardized processing of displacement signals by the LVDT transmitter LTM-6A-I includes:

- Linearization correction: The S-curve is converted into a perfect straight line through the 256-point calibration table stored in the EPROM

- Range matching: Supports 0-5V/1-5V/4-20mA multi-mode output

- Fault self-diagnosis: Real-time monitoring of coil impedance (normal range: primary 50Ω±5%, secondary 100Ω±10%)

III. Analysis of typical application scenarios

1. Closed-loop control of the regulating valve

In the DEH system, the displacement transmitter LTM-6A-I feeds back the regulating valve displacement to the controller in real time to form a PID regulation loop. The system response time is <20ms, the positioning accuracy is ±0.05mm, and the power load adjustment rate reaches 12MW/min.

2. Pull valve test support

After overhaul, through the S-shaped test curve of 0%→100%→0%, it can detect:

- Dead zone range (allowable <0.3%)

- Hysteresis (standard <0.5%)

- Linearity (required >0.998)

IV. Triple redundancy design: create a monitoring network that never fails

In the critical scenario of turbine valve control, the LTM-6A-I transmitter adopts an innovative triple redundancy architecture to build a three-dimensional protection system of physical layer, signal layer and energy layer.

At the hardware redundancy level, two LVDT sensors are installed on the valve linkage mechanism at an angle of ±45°, and displacement synchronization acquisition is achieved through mechanical card slots. When the data deviation of the main sensor exceeds 0.5mm, the system automatically switches to the backup sensor, and the switching time is less than 2ms to ensure the continuity of the control command. The signal redundancy system cross-validates through two independent AD conversion channels. When the difference between the two signals exceeds 0.3%FS, the self-calibration program is triggered to effectively avoid the risk of single channel failure.

In the control of the main steam isolation valve of the steam turbine, the LTM-6A-I transmitter has demonstrated excellent performance. The device controls the wedge gate valve with a diameter of 1.8 meters through a triple redundant configuration, with a displacement measurement accuracy of ±0.02mm, and can complete the full stroke closing of the valve body within 300ms.

When looking for high-quality, reliable LVDT transmitters, YOYIK is undoubtedly a choice worth considering. The company specializes in providing a variety of power equipment including steam turbine accessories, and has won wide acclaim for its high-quality products and services. For more information or inquiries, please contact the customer service below:

E-mail: sales@yoyik.com
Tel: +86-838-2226655
Whatsapp: +86-13618105229

Yoyik offers various types of spare parts for steam turbines, generators, boilers in power plants:
Load Cell part CS05721OL
Hydraulic valve F3DG5S2-062A-220DC-50-DFZK
Sensor Shear Pin X-F25-L105
MODUL MVC196E-01
Speed sensor A5S0DS0M1415B50-5M
Control SystemLVDTsensor 4000TDGNK
PLC XGK-CPUE
LVDTsensor LVDT1000-004
Transmitter S3(T)-RD-3AT-105A40Y
SPEED MONITOR XJZC-03A/Q
Linear Displacement Transducer for STG TDZ-1-02
TRANSMITTER AWT420.A.1.A1.C2.Y0.Y0.E511072
non contact linear displacement sensor TD-1-50
speed probe 1071/2
High Voltage fuse N2-24/0.5
RTD WZPM-001D
Proximity Switch E2E-X10MY1
pt 100 temperature WZPM2-201T
LVDT Sensor 3000TDGN-100-01-01
speed sensor CS-1-G-100-02-01
Fuse RT36-2(NT2)
Servo Card SFW-S(B)
Purging device HSDS-40/LQ
TRANSFORMER THEMOMETER BWR-04AJ
Lamp regulator OT 110/170…240/1A0 1DIMLT2 G1 CE
Gbr (Limit Switch)For Screws XCK-J0541
protect unit 7SJ6241-5EB90-3FE0
Tep. Metter BWR-04J(TH)
sensor BTLD 3B