Operation, Power Overloads, DC Disconnect

Chapter 8: Power Over Ethernet Overview

Operation

During normal operation, the PSE provides 44-57 VDC, able to support a minimum of 15.4 watts power.

Power Overloads

The IEEE 802.3af standard defines handling of overload conditions. In the event of an overload (a PD drawing a higher power level than the allowed 12.95 Watts), or an outright short circuit caused by a failure in cabling or in the PD, the PSE must shut down power within 50 to 75 milliseconds, while limiting current drain during this period to protect the cabling infrastructure. Immediate voltage drop is avoided to prevent shutdown due to random fluctuations.

Power Disconnection Scenarios

The IEEE 802.3af standard requires that devices powered over Ethernet be disconnected safely (i.e. power needs be shut down within a short period of time following disconnection of a PD from an active port).

When a PD is disconnected, there is a danger that it will be replaced by a non-PoE- ready device while power is still on. Imagine disconnecting a powered IP phone utilizing 48 VDC, then inadvertently plugging the powered Ethernet cable into a non- PoE notebook computer. What's sure to follow is not a pretty picture.

The standard defines two means of disconnection, DC Disconnect and AC Disconnect, both of which provide the same functionality - the PSE shutdowns power to a disconnected port within 300 to 400ms. The upper boundary is a physical human limit for disconnecting one PD and reconnecting another.

DC Disconnect

DC Disconnect detection involves measurement of current. Naturally, a disconnected PD stops consuming current, which can be inspected by the PSE. The PSE must therefore disconnect power within 300 to 400 ms from the current flow stop. The lower time boundary is important to prevent shutdown due to random fluctuations.

AC Disconnect

This method is based on the fact that when a valid PD is connected to a port, the AC impedance measured on its terminals is significantly lower than in the case of an open port (disconnected PD).

198	GE-DS-242-PoE Managed Ethernet Switch User Manual

GE-DS-242-POE specifications

The Graco GE-DS-242-POE is an advanced electric diaphragm pump designed to cater to a wide range of industrial applications. This model stands out for its reliability, efficiency, and innovative technology, making it an ideal choice for demanding environments such as automotive, food processing, and chemical handling.

One of the main features of the GE-DS-242-POE is its robust construction. Built from durable materials, it is designed to withstand harsh operating conditions, ensuring a long service life. The pump is powered by a reliable electric motor that guarantees consistent performance with minimal downtime. This electric design offers a significant advantage over air-operated pumps, as it eliminates the need for compressed air, reducing operational costs.

The GE-DS-242-POE utilizes a double-diaphragm design that allows for precise fluid transfer and improved efficiency. This technology enables the pump to handle a variety of fluids, including viscous materials, slurries, and abrasive substances, without compromising performance. The dual diaphragm feature also enhances the pump's ability to handle fluctuating pressures, making it suitable for diverse applications.

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Ease of maintenance is a crucial aspect of the GE-DS-242-POE. The design incorporates accessible service points, which simplify routine inspections and repairs. This user-friendly approach reduces maintenance time and costs, ultimately boosting productivity.

Additionally, the GE-DS-242-POE is equipped with advanced safety features. These include pressure relief valves and electronic controls that help prevent overpressurization, ensuring safe operation under all conditions. The pump also meets various industry standards, reinforcing its reliability and suitability for compliance with safety regulations.

In conclusion, the Graco GE-DS-242-POE is a technologically advanced electric diaphragm pump that excels in performance, durability, and versatility. Its robust construction, efficient double-diaphragm technology, and user-friendly design make it an indispensable tool for businesses in various sectors, enhancing operational efficiency while ensuring safety and reliability in fluid handling processes.

Graco GE-DS-242-POE Operation, Power Overloads, Power Disconnection Scenarios, DC Disconnect

Models: GE-DS-242-POE