Whether in the chemical, petrochemical, or steel industry, production plants and systems are the most important assets in all areas. This is the reason why the 24 V power supplies must always function perfectly no matter how adverse conditions are. The dip-coated Quint Power modules with preventive function monitoring and SFB technology therefore offer a high degree of reliability in the production environments of the process industry – and that even at 100 % air humidity and in the presence of corrosive gases.
The author: Anja Moldehn Marketing Power Supplies, Phoenix Contact Electronics
A protective coating is always applied to electronic modules that have to operate reliably even under very harsh conditions. The failure of critical applications – for example as a result of electrochemical migration or corrosion-related creepage currents – must be avoided at all costs. In the case of electrochemical migration, temperature and humidity combine to form a film of moisture on the PC board. This reduces the surface resistance and consequently also the insulating capability. Printed circuit board tracks and soldering materials are attacked to such an extent that they lose their contact properties and conductivity, resulting in device failure. Corrosion-related creepage currents or interruptions can occur at copper contacts – especially in atmospheres containing sulphur with a relative air humidity of more than 60 %. Values in this order are not unusual in industrial plants and systems.
These are just a few of the problems that can cause electronic modules to fail. One thing is clear, however: high humidity is responsible for the majority of them. Coating the modules protects against this type of failure, which is why achieving an optimum, seamless coating is of decisive importance. For this reason, Quint Power power supplies are given a thin protective coating in a dipping process. Even difficult-to-reach locations are reliably coated in this way and full coverage is guaranteed. Dipping allows the coating to be effectively applied to the contours of the electronic device.
Operation even at 100 % humidity
In contrast to spray coating, dip coating completely coats wired components such as bridge rectifiers and power semiconductors – as well as the underside of components, hollow spaces and the edges of PC boards. The Quint Power power supplies, which have an adjustable output voltage of 18 to 29.5 V DC and an output current of 5, 10 or 20 A, therefore function perfectly even at 100 % humidity. Three single-phase devices supply input voltages from 85 to 264 V AC or 90 to 350 V DC, while the three-phase module with 20 A rated output current can be operated from a mains supply with 3 x 320 to 575 V AC or 450 to 800 V DC.
With an efficiency of up to 93 %, the heat loss of these power supplies is minimal. This not only saves energy but also extends the service life of the components. The housing has a width of 40, 60 or 90 mm for the single-phase devices and 69 mm for the three-phase power supply. All the devices are 130 mm high with a mounting depth of 125 mm. The wide temperature range from -25 to +70 °C allows them to be used in a diverse range of applications.
In addition to the usual industrial approvals, the dip-coated modules with rated currents of 5 and 10 A also conform to DIN EN 60079–15 (Atex directive). As a result of this, they can be installed in hazardous areas in which Category 3G equipment is required (II 3 G Ex nA nC IIC T4 Gc). The devices have supplementary certification in accordance with IEC Ex (Ex nA nC IIC T4 Gc). All the power supplies in the Quint Power family comply with UL standard ANSI / ISA 12.12.01 as well as with the specifications for Class I, Division 2, Groups A, B, C and D (hazardous locations).
Dynamic power reserves
In many control cabinets used in the process industry, several sensors and actuators are connected to the power supply parallel to the control system. In order to minimise downtime, each of these circuits on the secondary side should be individually protected. If a short-circuit does occur, only the faulted circuit is disconnected from the power supply while the other loads continue to operate without any interruption. Commercially available circuit breakers have proven themselves to be a cost-effective solution for primary and secondary protection.
Quint Power devices clocked on the primary side trip the circuit breakers magnetically in just a few milliseconds. A power supply with rated values of 24 V and 20 A that supplies a control system as well as three additional loads is shown here as an example. Each circuit is protected by a 16 A circuit breaker (B characteristic). With AC voltage, the 16 A circuit breaker will trip magnetically at 80 A. If a DC application is involved, a correction factor of 1.5 must be taken into consideration: the circuit breaker therefore requires 120 A in order to trip reliably. In this example, if a short-circuit occurs because of a damaged cable, the 20 A power supply supplies six times the rated current (i.e. 120 A) for 12 ms using its selective fuse-breaking technology (SFB). The circuit breaker always trips reliably within three to five milliseconds in the magnetic range of its characteristic, while all the other loads continue to be supplied. The control system is supplied continuously and operates without any interruptions in spite of the short circuit that has occurred.
The dip-coated power supply units equipped with SFB technology provide 30, 60 or 120 A in the event of a short circuit and therefore trip B6 or B16 circuit breakers, for instance. Details of the cable lengths and cross-sections can be found in a configuration matrix on the Phoenix Contact website.
Preventive function monitoring
The high degree of flexibility that is required when engineering large plants and systems, as well as for ongoing optimisation and expansion, makes it absolutely essential that the power supplies have a certain power reserve. The three single-phase Quint Power power supplies mentioned above supply 7.5 A, 15 A or 26 A at a constant voltage with the static Power Boost power reserve. Power Boost is continuously available up to an ambient temperature of 40 °C. At higher temperatures, it can be activated for approximately ten minutes. High inrush currents of capacitive loads can therefore be handled without any voltage dips, for example.
In order to achieve high plant or system availability, Quint Power power supplies are equipped with preventive function monitoring for remote diagnostics. By permanently monitoring the output voltage and current, critical situations are signalled directly, both locally and to the control system. The power supply indicates the state by means of an LED, a floating relay and active signal outputs before potential problems have a chance to occur.
If the power supply is supplying more than the specified rated current, it is operating in Power Boost mode. Both the power supply and the connected loads are operating normally and the output voltage is 24 V DC. If the load is now further increased or if the ambient temperature rises, the 24 V supply will dip. This critical operating state is displayed, so that imminent faults can be identified before it is too late. If a conveyor belt with a mechanical problem has been localised, for example, it can be repaired before other loads experience voltage dips.
Online-Info: www.cpp-net.com/0311454
Share:
