The Role of the Three-Speed Sensor in Diesel Engine Protection Sensors

The Role of the Three-Speed Sensor in Diesel Engine Protection Sensors

 

The Function of the Oil Pressure Sensor, One of the Diesel Engine Protection Sensors

https://www.zwcummins.com/info/the-function-of-one-of-the-diesel-engine-prote-103620389.html

 

The Function of the Coolant Temperature Sensor, Another Diesel Engine Protection Sensor

http://The role of water temperature sensor (Two)- sensor in diesel engine protection

 

The first two articles explained the functions of the oil pressure sensor and the coolant temperature sensor. Today, we will talk about the function of the speed sensor.

 

The core of the speed sensor (tachometer sensor) is to collect the engine crankshaft speed signal, providing a speed reference for the controller and the governor system. It is the core acquisition component for unit speed regulation, protection, and grid connection.

 

Ⅰ. Core Functions

1. Real-time monitoring of engine speed: senses flywheel ring gear pulses, converts them into voltage/frequency signals, the controller calculates the actual speed, and the display shows the speed in real-time.

2. Electronic speed control (most critical): the governor compares the measured speed with the set rated speed, and the difference drives the actuator to adjust the throttle:

- Speed too high → reduce fuel supply to slow down

- Speed too low → increase fuel supply to speed up

Ensures frequency stability during no-load/load conditions (50Hz corresponds to 1500 rpm).

 

3. Overspeed Safety Protection: When the speed exceeds 110%~115% of the rated speed, the controller triggers an overspeed shutdown to prevent runaway, crankshaft fracture, or catastrophic engine failure.

 

4. Low-Frequency/Stall Protection: A sudden increase in load or insufficient fuel supply can lead to excessively low speed, triggering a low-frequency alarm/shutdown to prevent damage to electrical equipment from inadequate output voltage frequency.

 

5. Essential Signals for Synchronized Parallel Operation: Paralleled units rely on speed signals to adjust speed, achieving frequency and phase synchronization between two units for safe parallel output.

 

6. Timing and Operating Condition Judgment: The controller uses speed to determine whether the unit has successfully started, is idling, or operating under load, distinguishing startup faults (starter turns but the engine does not ignite).

 

II. Common Types and Installation Locations

 

- Magnetic-electric speed sensor: mainstream, installed on the flywheel housing, aligned with the flywheel ring gear, does not require power, outputs pulses by cutting magnetic lines of force; - Hall sensor: requires power, signal is more stable, strong anti-interference, mostly used in high-end units.

 

3. Consequences of failure:

 

Sensor damage/breakage: without speed signal, issues such as inability to adjust speed, false triggering of overspeed protection, stop immediately after start, unable to connect to the grid, speed display returns to zero, etc., may occur.