BECKHOFF EL9xxx System Terminal Guide

Beckhoff EL9xxx System Terminal Selection and Engineering Guide

In the EtherCAT terminal system, the vast majority of users focus on "functional" terminals such as digital input/output, analog acquisition, or motion control. However, a reliable, maintainable, and safety compliant automation system often relies on those silently working "system terminals" - they are responsible for power feeding, potential isolation, shielding grounding, E-bus current enhancement, surge protection, and energy storage buffering. Beckhoff categorizes these types of terminals as the EL9xxx series, which includes end caps, feed terminals (24 V DC/230 V AC), potential distribution terminals, shielding terminals, E-bus power feed terminals, surge filters, and buffer capacitor terminals.

This article is aimed at automation system integration and on-site maintenance engineers, systematically reviewing the technical parameters, internal wiring, installation location requirements, "non-interference" characteristics related to TwinSAFE safety applications, special conditions for explosion-proof (ATEX/IECEx/cFMus), and common design misconceptions of various models in the EL9xxx series. Whether you are renovating an old Woodward controller or planning an EtherCAT network for a new production line, selecting these system terminals correctly will significantly improve the reliability, anti-interference ability, and safety of the system.

End and isolation terminals: EL9011, EL9012, EL9080

1.1 EL9011/EL9012- Bus End Cover Plate

The rightmost end of each EtherCAT terminal station must be equipped with an end cover plate to provide mechanical protection and ESD protection. EL9011 has a width of 8mm (effective alignment width of 5mm), while EL9012 has a width of 8mm but a slightly higher height (55mm). Both do not have any electrical function and only serve as physical end caps. EL9011 is suitable for standard shell depths (34   mm), while EL9012 is suitable for deeper terminals (such as power terminals). Without an end cover, it can cause E-bus signal reflection, unstable communication, and may damage the spring contact of the last terminal.

1.2 EL9080- Potential Separation Terminal

EL9080 is used to interrupt power contacts while the E-bus continues to pass through. The orange front panel clearly indicates the interruption of power contacts. When it is necessary to mix different voltage groups within the same terminal station (such as a 24V DC power contact on the left and a 230V AC power contact on the right), EL9080 must be inserted for electrical isolation. Otherwise, short circuits may occur between potential groups of different voltages, damaging equipment or causing fires.

Feed terminal: EL9100、EL9110、EL9150、EL9160、EL9190、EL9200、EL9210、EL9250、EL9260、EL9290

The feeding terminal is used to establish a new potential group at any position of the terminal station or to supplement the power supply for high current applications. They introduce external power into the power contacts, while the E-bus is transparently transmitted.

Model Rated Voltage Diagnostic Function Fuse Special Instructions

EL9100 24V DC without standard feed

EL9110 24V DC has (1 diagnostic bit) and no diagnostic bit indicating normal power contact voltage

EL9190 230V AC/DC None Suitable for AC or DC high voltage (up to 230V)

EL9150 230   V AC (120   V AC) without AC power supply

EL9160 230   V AC (120   V AC) with (1) no diagnostic position "PowerOK"

EL9200 24V DC without 6.3 A built-in fuse overcurrent protection

EL9210 24V DC with (2 bits: PowerOK+FuseError) 6.3 A fuse status readable

EL9250 230   V AC without 6.3   A AC with fuse

EL9260 230   V AC with (2 digits) 6.3   A diagnosis PowerOK+FuseError

EL9290 230   V AC (variable) No universal high voltage feed, no fuse

Key wiring: All feeding terminals are provided with two sets of parallel input terminals (for example, terminals 1 and 4 of EL9100 are both+24   V, terminals 2 and 5 are both 0   V, and terminals 3 and 6 are both PE), allowing for loop in and loop out. When it is necessary to transmit the same power supply to multiple terminals on the right side, this feature can be used to reduce external jumpers.

Diagnostic function usage: The process images of EL9110, EL9160, EL9210, and EL9260 contain diagnostic bits. In the TwinCAT tree, these terminals will display "PowerOK" and/or "FuseError" variables. If the voltage is lower than about 17   V (for a 24   V system), PowerOK becomes False; If the fuse blows, FuseError becomes TRUE. It is recommended to monitor these bits in the PLC program and trigger alarms or safety shutdowns in case of faults.

Explosion proof environment precautions: When using power supply terminals in ATEX Zone 2 or Class I Division 2 areas, fuses must be replaced only in a power-off or non explosive environment (for EL9200/9210/9250/9260).

Potential distribution terminals: EL9180-EL9189

When it is necessary to extend the power contact voltage to multiple sensors or actuators, using potential distribution terminals can avoid external wire terminal blocks.

Model, Terminal Point, Potential Number, Description

EL9180 8 terminal points (internal paired connection) 1 (positive pole+negative pole+PE all lead out) Standard shell, each contact can be connected to ≤ 10 A

EL9181 16 terminal points (divided into two groups, with 8 internal connections in each group) 2 independent potential HD shells, direct plug-in technology

EL9182 16 terminal points (8 independent channels), each with one potential, suitable for multiple different signals

EL9183: Large scale distribution of all 16 terminal points connected to a single potential

EL9184 16 terminal points: 1-8 for+24   V, 9-16 for 0   V 2 (positive and negative) HD housing, dedicated to 24   V systems

EL9185 8 terminal points (1, 2, 5, 6 for+24   V; 3, 4, 7, 8 for 0   V) 2 standard housing with 4 additional connection points to power contacts

EL9185-0010 is the same as EL9185, but the power supply contact on the right side (forming a new potential group) 2 can interrupt the input of the left power supply contact and re feed

EL9186 8 terminal points (all connected to positive power contact) 1 positive output only

EL9187 8 terminal points (all connected to the negative power contact) 1 negative output only

EL9188 16 terminal points (all+24   V) 1 HD shell, 16 positive poles

EL9189 16 terminal points (all 0   V) 1 HD shell, 16 negative poles

HD (High Density) shell features: The width is still 12mm, but it provides 16 wiring points. Solid wires can be directly inserted (without tools), while thin stranded wires require a screwdriver to press the spring. Wire cross-section: solid 0.08... 1.5   mm ², stranded 0.25... 1.5   mm ², with tubular ends 0.14... 0.75   mm ².

Important limitation: The PE contact of EL9180 is coupled to the DIN rail through capacitance, so the PE feeder must be disconnected during insulation testing, otherwise it may cause misreading or damage to the terminal.

Shielded terminals: EL9070 and EL9195

4.1 EL9070

EL9070 provides 8 shielded wiring points, all of which are connected internally to the mounting rail. Its inner surface is a continuous copper layer, which can form good shielding isolation between the two EtherCAT terminals. Suitable for centralized grounding of multiple shielding layers, avoiding the use of additional grounding terminal blocks. The rated voltage is arbitrary (up to 230   V AC/DC), and the current load is 10   A. Note: EL9070 is not connected to the power contacts, only to the PE (through the guide rail). The working temperature range is 0... 55 ° C (non extended temperature).

4.2 EL9195

EL9195 is a high-voltage shielded terminal that also directly connects the spring contacts to the DIN rail, but simultaneously transmits two power contacts (positive and negative). Allow the power supply voltage to be transmitted to the right terminal while shielding the ground. It is suitable for 230V AC/DC systems. Internal wiring: Terminals 1 and 5 are connected, 2 and 6 are connected (positive pole), 3 and 7 are connected (0   V/N), and 4 and 8 are connected (shielded/PE). In the design of mixed voltage groups, EL9080 must be used for potential separation.

E-bus power input terminals: EL9400 and EL9410

The E-bus is provided by a coupler, with a maximum of 2 A (5 V). When the terminal station is too long or contains terminals with high current consumption (such as certain communication modules or high-precision analog terminals), the E-bus current may be insufficient. The E-bus current calculation in TwinCAT System Manager will display negative values and exclamation marks, and EL9400 or EL9410 must be inserted before the current depletion point.

EL9400: Pure power input, no diagnosis, requires external supply of 24V DC, outputs 2A to E-bus. At the same time, it also transmits power contacts (24V), which can be used to establish new potential groups.

EL9410: Added diagnostic function, indicating whether the E-bus voltage (Us) and power contact voltage (Up) are below 17V through LED and process mapping (2 bits: Us undervoltage, Up undervoltage). Its RUN LED also displays the EtherCAT state machine status (Initiat, PREOP, SAFEOP, OP, BOOTSTRAP).

Wiring: Terminals 1 and 5 of EL9410 provide power to the E-bus (+24   V and 0   V are used for internal DC/DC), while terminals 2/6 and 3/7 are used for the+24   V and 0   V loops in and out of the power contacts, respectively. Be sure to use the same ground potential, otherwise E-bus communication may be abnormal.

Surge filter terminal: EL9540/EL9550 series

In harsh electromagnetic environments such as ships, wind power, and offshore platforms, surge voltage may be generated on power lines due to lightning strikes or inductive load switching. The EL9540/EL9550 series terminals provide conducted surge protection.

Special Instructions for Diagnosis of Rated Current of Model Protection Object

EL9540 only provides on-site power supply (Up) of 10A without standard temperature range of 0... 55 ℃

EL9540-0010 is only available for on-site power supply of 5   A (under voltage/over-voltage diagnosis) and is particularly suitable for analog terminals, with a working temperature of -25...+60 ℃

EL9550 system power supply (Us)+on-site power supply (Up) Us ≤ 1.5 A (HW ≥ 03), Up ≤ 10 A, total not exceeding 10 A No old models

EL9550-0010 system+on-site, with currents of up to 10 A each (total 10 A) and 4 bits (Up/Us undervoltage/overvoltage), suitable for high current devices such as CX embedded PCs

EL9550-0012 system+on-site, each with 10 A independently, no higher capacity

Diagnostic application: EL9540-0010 provides "Undervoltage" and "Overvoltage" bits (1 bit each) in the process image. EL9550-0010 provides 4 digits (Up Undervoltage, Up Overvoltage, Us Undervoltage, Us Overvoltage). When the voltage is below 18V or above 30V, the corresponding bit becomes TRUE. By utilizing this information, it is possible to safely shut down the output or record events in the event of abnormal voltage.

Installation location: The surge filter should be placed as close as possible to the power inlet. The manual provides application examples: EL9550 supplies power to couplers and digital terminals, and EL9540 supplies power to analog terminals, forming a two-layer protection.

Buffer capacitor terminal: EL9570

The EL9570 has a built-in 500 µ F capacitor with an internal resistance of<10 µ m Ω, which is used to smooth power supply voltage fluctuations and absorb regenerative energy. Typical applications include parallel connection with stepper motor terminals (EL7041), DC motor terminals (EL7342), or servo motor terminals (EL7201). When the motor decelerates, the regenerated energy will increase the DC bus voltage, and EL9570 absorbs this energy; If the voltage exceeds 55   V, the internal circuit will connect to an external braking resistor (recommended 10   Ω/10   W) to consume excess energy. The overload LED (green) stays on when energy is absorbed by the resistor.

Attention: The rated voltage of EL9570 is 50   V and cannot be used for 230   V systems. Its power contacts on both sides are straight through, but there is no PE contact on the left side. Multiple motors can share one EL9570, but the total regenerative energy needs to be calculated.

Interference free terminals in secure applications

In TwinSAFE safety applications, certain standard terminals are classified as' interference free ', meaning they do not affect the safety integration level (SIL/PL). But when using, it must meet the hardware version requirements (see tables on pages 15-16 of the manual, such as EL2004 starting from hardware version 15, EL2809 starting from 01, etc.). In addition, external wiring must eliminate short circuit faults, including:

Use independent sheathed cables (different potentials do not share the same sheath)

Only wiring within the same control cabinet

Each wire has independent grounding protection

Permanent fixation of cables and prevention of external damage

If the "ground feedback+full pole cut-off" measures are used, the maximum can reach Cat.4/PL-e/SIL-3.

Key: In a potential group, all terminals must be interference free, and external circuits cannot provide energy feedback even under fault conditions.

Rules for placing passive terminals

The so-called passive terminal refers to terminals that do not participate in active data exchange and do not consume E-bus current, such as EL9011 (end cover), EL9080 (potential separation), EL9070 (shielding), EL9180 and other potential distribution terminals, EL9400/9410 (E-bus feeding), and EL9540/9550 (surge filter). To ensure the integrity of the E-bus signal, no more than two passive terminals should be connected in series. If more passive terminals must be connected after two passive terminals, an active terminal (such as EL1004 digital input) should be inserted in the middle. Otherwise, it may cause data delay or errors.

Installation and wiring specifications

10.1 DIN rail installation

All EL9xxx terminals are installed on a 35 mm guide rail (EN 60715). The steps are as follows:

First, hang the coupler (such as EK1100) onto the guide rail.

Push the terminal into the slot from the right side until the locking buckle clicks into place. It is strictly prohibited to first clamp the guide rail and then push it laterally, otherwise it will damage the power contacts and E-bus spring.

When disassembling, pull the orange buckle strap by about 1cm to release the buckle, and then pull out the terminal.

10.2 Enhance mechanical load capacity

For applications with severe vibration (such as ships and vehicles), TH35-15 guide rails should be used, with mechanical fasteners clamped at both ends. The total number of terminals should not exceed 64 (12mm width) or 32 (24mm width), and the distance between guide rail fixing points should be ≤ 5cm. Terminals such as EL9100, EL918x, EL9400, etc. all support reinforced mechanical loads.

10.3 Wiring Techniques

Standard spring terminal (ELxxxx): Insert a screwdriver vertically into the square hole, press in the wire, and then remove the screwdriver. The cross-sectional area of the wire is 0.08... 2.5 mm ², and the stripping length is 8-9 mm.

HD terminals (EL9181/2/3/4/8/9): Solid wires can be directly inserted into circular holes without the need for tools; The fine twisted wire needs to be pressed with a screwdriver. The stripping length is 8-9mm.

Shielded connection: The shielded terminals of EL9070 and EL9195 are directly pressed into the bare wire of the shielding layer, and the other end is connected to the guide rail.

10.4 Potential group and insulation testing

When mixing 24V and 230V power contacts at the same terminal station, EL9080 must be inserted between different voltage groups. Before conducting insulation tests (such as voltage withstand tests on 230V circuits), all PE feeders should be disconnected, as coupling between PE contacts and rail capacitors may cause the tester to misjudge.

Explosion proof special conditions (ATEX/IECEx/cFMus)

Many EL9xxx terminals (EL9011, EL9100, EL9180, EL9195, EL9400, EL9540, etc.) have obtained explosion-proof certification. When using in Zone 2 or Class I Division 2 areas, the following must be followed:

Installed in an enclosure with at least IP54 rating.

Pollution level ≤ 2, transient overvoltage ≤ 119   V (for 24   V systems) or 140% of rated voltage.

Temperature range: Standard terminal 0... 55   ℃; Extended temperature (ET) terminal -25...+60 ℃.

Do not plug or unplug while live, and do not adjust fuses or wiring in explosive environments.

For feed terminals with fuses (such as EL9200), power must be disconnected before replacing the fuse.

Please refer to the nameplate on the side of the terminal for specific explosion-proof markings (such as II 3 G Ex nA IIC T4 Gc).

Diagnosis and troubleshooting checklist

Possible causes and solutions for the phenomenon

E-bus communication interruption, RUN LED off, end not installed with EL9011/EL9012, end cover installed

The power contact voltage is normal, but there is no power supply potential group at the downstream terminal. The EL9080 is interrupted or not fed. Check if EL9080 is inserted; If necessary, install a feeding terminal on the right side

The FuseError of EL9210 in TwinCAT is TRUE. After the internal fuse is blown and the power is cut off, replace the 6.3-A slow melting fuse (only applicable to EL9200/9210/9250/9260)

The Diagnosis LED (Us) of EL9410 has a red E-bus power supply voltage below 17V. Check the 24V input of EL9410; Measure the voltage at 1/5 of the terminal

The analog signal fluctuates greatly, and EL9540-0010 reports overvoltage power supply line surge or poor voltage regulation. Add EL9550 or external surge protector at the front end

Motor regeneration energy causes overvoltage alarm (EL9570 overload LED is always on). The regenerated energy exceeds the capacitor capacity, and the braking resistor is not connected to the 10 Ω/10 W braking resistor

Standard terminals in security applications affect PL level. Non interfering terminals are not used or hardware versions are too low. Check the hardware version number; Adopting grounding feedback and full pole cut-off wiring