What is the maximum power output of a PoE injector?

Maximum Power Output of a PoE Injector

The maximum power output of a PoE injector refers to the amount of electrical power it can deliver to a Powered Device (PD) over an Ethernet cable. This power is essential for ensuring that network devices requiring both data and power (such as IP cameras, wireless access points, or VoIP phones) can operate correctly without the need for separate power cables.

PoE injectors follow IEEE standards for power delivery, and the maximum power output depends on the specific PoE standard being used. Here’s a detailed breakdown:

1. IEEE 802.3af (PoE) – 15.4W per port

Maximum Power Output at PSE (Power Sourcing Equipment):

--- 15.4 watts is the maximum power that a PoE injector (PSE) can supply to a Powered Device (PD).

--- Power Delivered to PD: The actual power that reaches the powered device is typically around 12.95W due to losses in the Ethernet cable.

Specifications:

--- Voltage: 44V to 57V DC

--- Current: Maximum 350mA

--- Power Delivered to PD: 12.95W (considering losses over the Ethernet cable)

--- Common Use Cases:

--- Basic IP cameras

--- VoIP phones

--- Simple wireless access points (WAPs)

--- Low-power IoT devices

--- Small sensors

2. IEEE 802.3at (PoE+) – 30W per port

Maximum Power Output at PSE (Power Sourcing Equipment):

--- 30 watts is the maximum power that a PoE injector (compliant with IEEE 802.3at) can deliver to a device.

--- Power Delivered to PD: Typically around 25.5W, after accounting for losses.

Specifications:

--- Voltage: 50V to 57V DC

--- Current: Maximum 600mA

--- Power Delivered to PD: 25.5W (considering losses over the Ethernet cable)

Common Use Cases:

--- PTZ (Pan-Tilt-Zoom) cameras

--- Advanced wireless access points (WAPs)

--- Video-capable VoIP phones

--- Digital signage

--- Small network switches

3. IEEE 802.3bt (PoE++ or 4PPoE) – 60W to 100W per port

IEEE 802.3bt is the latest standard, and it provides two types of power outputs:

--- Type 3 (PoE++) – 60W per port

Maximum Power Output at PSE: 60W per port is the maximum power that can be delivered by a PoE injector.

--- Power Delivered to PD: Typically around 51W (due to power loss).

Specifications:

--- Voltage: 50V to 57V DC

--- Current: Up to 960mA

--- Power Delivered to PD: 51W (considering losses over the Ethernet cable)

Common Use Cases:

--- High-performance wireless access points (Wi-Fi 6)

--- PTZ cameras with heaters/blowers

--- Digital signage (larger displays)

--- LED lighting systems

--- Smart IoT devices

--- Type 4 (PoE++ or 4PPoE) – 100W per port

Maximum Power Output at PSE: 100W per port is the maximum power that a PoE injector can supply.

Power Delivered to PD: Typically around 71W (accounting for losses).

Specifications:

--- Voltage: 50V to 57V DC

--- Current: Up to 1.5A per pair (since Type 4 uses all four pairs in an Ethernet cable)

--- Power Delivered to PD: 71W (considering losses over the Ethernet cable)

Common Use Cases:

--- Wi-Fi 6E access points (the next generation of wireless technology)

--- Large digital signage displays

--- High-power devices like advanced IP cameras (including PTZ)

--- Edge computing devices

--- LED lighting systems for large areas

4. Passive PoE

Maximum Power Output at PSE:

--- The maximum power output of passive PoE is not standardized. It typically ranges between 12V, 24V, or 48V, depending on the injector's design and manufacturer.

--- Unlike IEEE 802.3 standards, passive PoE does not use power negotiation and provides a fixed voltage. The maximum power delivered depends entirely on the specific model.

Common Use Cases:

--- Ubiquiti Networks devices like their wireless radios or access points.

--- Proprietary devices where specific voltage is required (e.g., some legacy networking equipment).

Comparison of Power Outputs:

Key Takeaways:

--- IEEE 802.3af (PoE) is ideal for low-power devices such as IP cameras and VoIP phones, with a maximum output of 15.4W.

--- IEEE 802.3at (PoE+) supports higher power demands, up to 30W, making it suitable for PTZ cameras and advanced access points.

--- IEEE 802.3bt (PoE++ or 4PPoE) offers Type 3 (60W) and Type 4 (100W) outputs, capable of powering high-demand devices like Wi-Fi 6 access points and large digital signage displays.

--- Passive PoE provides varying levels of power depending on the manufacturer, with no standardized voltage or power negotiation, often used for proprietary devices.

The power output of a PoE injector determines what devices it can power, so it’s crucial to choose an injector that matches the power requirements of the devices in your network. For high-wattage devices, PoE++ injectors (802.3bt) are essential, while lower-power devices may only require standard PoE (802.3af) injectors.