Breakers without borders

A typical place of operation for electronic breakers (eBreakers) is inside an industrial control panel, which has to comply in Europe with the Machinery Directive. EN 60204-1 is a practical standard, which should be used to meet the safety aims of this Directive.

One such is the usage of eBreakers (or solid state overcurrent protectors) at 24Vdc to comply with requirements for overcurrent and ground fault protection. These cover not just the control circuits, but also the strong and powerful power supplies that drive them.

The Machinery Directive and EN 60204-1 require overcurrent protection for control circuits and it is important to distinguish whether the circuit is earthed or not. At earthed branches, a protector has to be installed in each ungrounded conductor. If it is an unearthed circuit, it has to comply with one of the following aspects:

• If the circuit consists of the same wire diameter, only one protector has to be installed in that circuit
• If the circuit consists of different wire diameters, protectors have to be placed in each and the common feeding conductor.

Block electronic circuit breakers comply with European and US standards, and using eBreakers from the company's Power Mini and Power Compact series enable these requirements to be achieved very easily.

Both Power Mini and Power Compact series are evaluated for use with an SMPS as well as with high power transformer–rectifier combinations having rated DC currents of 250A and more. The low impedance short testing at rated ambient also complies comfortably with EN 60204-1. Furthermore, eBreakers are able to meet shutdown times with adjustable rated currents, which can be set up individually per channel individually (national requirements may be taken into account). Block's eBreakers are also feature a sealable cover to prevent from current settings from being interfered with.

US requirements are similar to European ones, but differ in some detail. The National Fire Protection Agency (NFPA) frequently updates the National Electrical Code (NEC); this refers to UL508A for industrial control panels. As EN 60204-1 defines protection of control circuits, UL508A does so similarly and overcurrent protection devices have to be installed in each un-grounded conductor.

Tolerable voltage dips

Maximum tolerable voltage dips must not be undercut for sensitive devices, which can lead to undesirable consequences for logic controllers or PLCs; this can happen when an adjacent circuit (powered by the same source but fused separately) fails and the output voltage of the supply goes down until the protective device of that failing circuit operates.

eBreakers shut down such short circuits much faster and more precisely, so resets cannot occur. The use of Block's Basic version of electronic fuses, which contain an active current limiting feature, means that sensitive loads can be used without any effect in the event of faults or short cicuits. No voltage dips at the output of the eBreaker will occur when a parallel channel is affected and has to be shut down.

Block Economy versions are also able to react fast and precisely, but due to missing current limiting features, voltage dips at all outputs will happen, depending on impedance characteristics of each channel. The Power Mini and Power Compact electronic breaker families are UL2367 recognized, UL508 listed and product type approved by Germanischer Lloyd (DNV-GL).

DIN rail power supplies for smaller power requirements

The single-phase PEL power supplies from Block cover lower power requirements from 25 to 100W. These units are designed with 12, 18 and 24V outputs, for applications such as installation distributors and small control panels.

The power supplies features a low profile design suitable for use in building automation. The output power is available up to an ambient temperature of +55C. The units are supplied in a robust and easy to fit DIN Rail plastic housing with spring clamps terminals for safe and easy connection. The range is UL, CUL and GL approved.