EUCHNER ESM-BA301 Safety Relay

Basic safety relay for emergency stop and guard circuits

The EUCHNER ESM-BA301 (order no. 085613) is a basic module from the ESM-BA3 safety relay series. It evaluates emergency stop buttons and safety switches and switches the machine load through three redundant, positively driven safety contacts. A fourth, normally closed contact is provided as an auxiliary or monitoring contact for signalling to a PLC or indicator.

EUCHNER rates the module for use up to category 4 according to EN ISO 13849-1. The input circuit can be wired for 1-channel or 2-channel control, and the device detects short circuits between the input cables as well as earth faults, shutting the outputs down or blocking a restart when such a fault is present. Two green LEDs show the state of the internal relays K1 and K2.

Technical specifications

EUCHNER states that the PL e characteristic values apply at a switching voltage of 24 V DC with limited switching current and annual switching cycles (for example up to 0.1 A at 500,000 cycles per year). Higher loads reduce the permitted cycle count, so check the operating instructions for the actual contactor load.

Wiring functions and start behaviour

The function of the module is set by the external wiring rather than by switches. Typical options are automatic start or start by pushbutton, monitored start, simultaneity monitoring of the two input channels, and feedback monitoring of downstream relays or contactors. Feedback monitoring means the normally closed auxiliary contacts of the load contactors are wired into the start circuit, so the relay cannot restart if a contactor has welded.

Control cables can be long: EUCHNER gives a maximum control cable length of 1000 m with a 0.75 mm² conductor, which suits large machines and conveyors where the emergency stop buttons are spread out.

Installation and thermal limits

Mount the relay in a control cabinet on a TH 35 rail. All connections must be supplied from a safety transformer or an equivalent isolated supply. When several ESM-BA3 modules are mounted side by side under load, the permitted cumulative current falls with temperature: 9 A at 20 °C, 3 A at 30 °C and 1 A at 40 °C. Above these values, leave a 5 mm gap between the devices. In hot cabinets this derating is often the deciding factor.

The relay is one part of the safety function. The overall performance level depends on the input devices, the wiring, the output contactors and the validation of the complete circuit.

Documents and quotation

The attached EUCHNER operating instructions cover the ESM-BA3 basic modules, including wiring examples and safety data. For a quotation, give the order number 085613, the quantity and whether a version with plug-in terminals is required. Other EUCHNER devices are listed under Safety Switches & Guard Locking.