48V DC electronic circuit breaker is 'world first'

Potential markets for the 48V DC devices include factory automation, printing machinery, test systems, process plant, telecommunications and renewable energy.

Many of the features of the 48V DC models are already found on the 24V models, but Murrelektronik highlights the following in particular:

• Tamper-proof rotary switches for adjusting current range
• Power on when starting capacitive loads
• Temperature-independent operating time
• Proven bridging system
• Non-volatile error memory
• LED status indicators, including when 90 per cent load is reached
• Remote status indication

Importantly, the switch-off behaviour has been optimised so that it is as early as necessary but as late as possible to avoid nuisance trips. Current range can be set at 1A, 2A, 3A or 4A, or 1A, 2A, 4A or 6A (depending on model) using the rotary switches on the front panel, which are protected by a tamper-proof cover. A further useful feature is the cascaded start-up that provides a delay of approximately 100ms between the channels to reduce inrush currents.

Systems that are characterised by capacitive loads - such as servo drives, fieldbus systems, analogue cards and control systems - can be protected by MICO 48V DC solid-state protective devices, as these are rated at 5000uF per channel (equivalent to 20,000uF at 24V DC).

Faster fault-finding

To support troubleshooting, the channel status is maintained even after a power reset, and the status is easily seen via the LEDs on the front panel. As previously mentioned, the 90 per cent warning helps in identifying problems before they cause stoppages or unnecessary wear of components such as motors and valves. The warning - at 90 per cent of tripping current - is signalled by a flashing LED at start-up and via a 20mA signal that can be monitored remotely. In addition, there is a group alarm contact for all channels on the MICO device for reporting overloads, short circuits and manual deactivation.

Machine builders, system integrators and end users concerned with energy consumption will appreciate the MICO's ability to be remotely controlled; all channels can be activated and deactivated by a 48V DC signal to save energy when equipment is not operating.

In applications where space is at a premium, or when smaller control cabinets are used to save costs, the space-saving nature of the MICO devices can make a significant difference. Whereas a bank of eight traditional circuit breakers would require 208mm of linear space, the same eight channels can be implemented using a pair of four-channel MICO devices requiring just 140mm, which is a reduction in space of approximately one-third.

In terms of reliability, the MICO overcurrent protection devices offer a further advantage in that their operation is independent of ambient temperature. Whereas traditional breakers are electromechanical devices that are influenced by temperature, the electronic MICO devices will always operate at the same point in any ambient temperature from -25 to +55degC.

Email [email protected] for more information about the MICO+ 48V DC electronic circuit breakers.