Diesel & Gas: Part 4 - 2 Pages

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Diesel & Gas: Part 4

Catalog excerpts

DIESEL AND GAS ENGINES ENGINES Speed measurement of Turbochargers A strong magnet and a coil system build the core of these sensors. The target is normally a disc which is located in the bearing section of the turbocharger. That disc has notches or holes so that the air-gap alters at these sections when the disc rotates with the turbo. The induced voltage is the desired output signal. Many different sizes and housings are available to adapt the sensors to the properties and specific mechanical needs of the application. Introduction Turbocharger speed mainly depends on the exhaust and the conditions under which the engine is running. Under certain circumstances the speed can reach critical values for the safety and lifetime of the turbocharger. As the need for higher pressure values and hence higher nominal turbo speeds has constantly increased over recent years it has become more and more important to know the instantaneous speed of the turbo. This is valid for nearly all sizes of turbochargers from the very small and fast rotating passenger car turbochargers up to the large units used in 2-stroke ship engines. There are 2 main concepts of sensors used in this application. VR-sensors looking at a target in the bearing section of the turbo and eddy current sensors aimed at the compressor wheel counting the blades. JAQUET is the world leader in speed sensor solutions for all turbocharger applications ranging from passenger cars, through truck and railway engine sizes right up to large turbos for ships’ engines. Well over 8 million of these sensors are reliably protecting turbochargers worldwide, day after day. The common features and properties of these sensors are: • • • • • Very robust and reliable construction Can withstand high temperatures (up to 320 °C) The amplitude of the output signal depends from the speed of the turbo. It is not possible to measure zero-speed condition. They actively produce an output signal without the need for a supply voltage. They can be delivered with mating connectors or with integral cables. Eddy Current Sensors The eddy current sensor aims at the compressor wheel of the turbocharger. The sensor creates a HF-field at its front end and generates a signal from every compressor blade that interacts with this HF-field. The main properties of this class of sensors are: • • • • • Sensor must be supplied with 10 .. 30 VDC Sensors with integral electronic can withstand temperatures -40 .. +125 °C Sensor head without electronic are capable up to +180 °C (the electronics can be placed in a separate terminal box which is located at a cooler spot). Sensor is capable to delivering speed information close to zero-speed. Output signal is a clear rectangular pulse stream that can be divided to 1 pulse per revolution.

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DIESEL AND GAS ENGINES ENGINES Tachometer with 1 or 2 channels T401 / T501 Many ECU’s are not capable ofeading frequencies over a value of about 5 .. 10 kHz. Turbocharger speed information – especially in the case of the HF-bladecounting technology – however reaches often higher values. One of the solutions is to use one of the T400 or T500 tachometer series. These all in one instruments allow frequency conversion into an analogue signal (to supply an external analogue indicator) as well as a frequency division and accurate over speed protection functionality. T400 as single channel unit,...

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