Designers or specifiers of AC/DC power supplies for industrial, plant, building and process automation, power generation and distribution, infrastructure, and data and telecommunications applications face numerous electrical, physical, deployment, maintenance, security, and compliance challenges. However, many of these difficulties can be overcome by carefully selecting an off-the-shelf DIN rail power supply and fuses designed for the above applications.
This paper provides a brief overview of the difficulties encountered in using these products. The DIN rail-mounted AC/DC and DC/DC power supplies of RECOM Power and the assorted fuse product line are then described. These products enable reliable and safe industrial grade DC power supply.
Challenges with industrial power supplies
The industrial application power supply must meet the following requirements: compact structure, capable of adopting various three-phase AC or high-voltage DC input, high efficiency, complying with many regulatory requirements, supporting parallel operation for redundancy, powerful user and system protection functions. In addition, such power supplies must meet performance specifications over a wide temperature range with only passive cooling, be robust, have a long mean time to failure (MTBF), and be cost effective in deployment and maintenance.
The operating conditions required for these applications preclude the feasibility of custom designs and outline specifications, and DIN rail-mounted power supplies and fuses are preferred. The current difficulties have turned to prudent selection to achieve application optimization.
Power supply: from package
The critical role of power supplies in system integrity is often overlooked. The core starting point of power supply design is packaging, which directly affects its electrical, mechanical and thermal performance in industrial environment. Therefore, the industrial power supply is designed for standard DIN rail installation in almost all cases (Fig. 1).
Industrial control cabinet with various modules mounted on DIN rail
Figure 1: Industrial control cabinet with various modules mounted on DIN rail, which can be easily removed from the front and can be wired at any time. Picture source: Hakaday)
DIN rails are fixed on the rear panel or enclosure of the equipment control cabinet. All electrical modules such as motor drives, loop controllers, power supplies, signal interfaces, safety subsystems, and communication interfaces are mounted on this rail and all power and signal connections are accessible from the front.
The DIN rail solution contrasts well with the 19 "rack, which is equipped with front and rear wiring ports for connecting modules. This rack is widely used in laboratory instrumentation and test/measurement systems. In contrast, DIN rails are more convenient and practical because a large number of modules often have to be installed in a cabinet, resulting in a space-limited awkward situation.
Many AC/DC power supplies in industrial applications use three-phase 320 VAC to 575 VAC line inputs and must provide a clean, stable, transient resistant 24 VDC or 48 VDC voltage to loads such as motor controllers. In addition, many applications today require 430 V to 815 V high voltage DC power supplies. The use of DC power supplies is ideal for micro-grid based plant automation applications and renewable energy solutions, including biogas, photovoltaic and wind energy equipment.
To meet the demanding requirements of industrial power supply via DIN rail mounted power supply, designers can use RECOM Power's three-phase RACPRO1 series AC/DC power supply. This series of power supplies can also be used for high voltage DC inputs.
For example, RAC1-T240/24, RAC PRO1-T480/24, and RAC PRO1-T960/24 (Figure 2, left to right) have an output power of 240 W, 480 W, and 960 W, respectively, and an output voltage of 24 V. In addition to these versions, 48 V output versions are available, but are otherwise identical. In addition, the rated output voltage of the series power supply can be adjusted from 24 V to 28 V and 48 V to 56 V.
RACPRO1-T240/24 (left), RACPRO1-T480/24 (middle) and RACPRO1-T960/24 (right) DIN rail power supplies of RECOM Power
Figure 2: Compact RACPRO1-T240/24 (left), RACPRO1-T480/24 (middle) and RACPRO1-T960/24 (right) DIN rail power supplies provide 240 W, 480 W and 960 W respectively. Image source: RECOM Power)
An important feature of this series of power modules is their compact shape. Specifically, each power module has a width of 43 mm, 52 mm, and 80 mm (1.69 ", 2.05", and 3.15 "). Each of these three modules has a height of 135 mm (5.31") and a depth of 140 mm to 156 mm (5.51 "to 6.14") depending on the model. An important feature of these modules for installers and technicians is the use of push-on cage clamps with+25 ° push-on connectors for fast and easy removal without the need for any tools.
RACPRO1 series has high efficiency, which can reduce operation cost and power heating. Therefore, a smaller radiator and cooling surface can meet the cooling requirements.
These power supplies do not require forced air cooling by fans or other active systems; Another advantage in industrial environments is the use of a fully natural convection cooled design. Each power module has two independent airflow flues to maximize "stack effect" for cooling.
Through ingenious layout and device selection, the series realizes small size and high efficiency. Efficiency of RACPRO1-T960/24 power supply is 96%; The efficiencies of the RACPRO1-T240/24 and RACPRO1-T480/24 power supplies are 94.1% and 95%, respectively. In addition, although these power supplies can output hundreds of watts, they require only about 1 W at no load.
Thanks to their excellent efficiency and cooling, these power supplies can withstand high operating temperatures. W RACPRO1-T960/24 power supply can provide rated full-load output power at temperature up to+60 ° C; The 240 W RACPRO1-T240/24 power supply operates at a slightly higher temperature of+70 ° C under the same output conditions.
High temperature is not the only issue to consider, and for many equipment such as outdoor HVAC equipment, it is also subject to extreme cold. To eliminate this effect, the rated operating temperature of the RACPRO1 power supply is - 40 ° C.
Electrical Performance and Function
Power supplies in industrial environments must not only provide nominal voltages at a variety of different input voltages and loads, but also have more functions. Other essential performance indicators include high back impulse voltage immunity, stronger surge immunity and power ascension capability:
When supplying or de-energizing non-resistive loads such as motors, a current return (also known as reverse feed) is generated and enters the output of the power supply. Backflush voltage immunity refers to the ability of the power supply to withstand the back flush voltage. In the RACPRO1 power supply, the 24 V output has a 35 V backshoot voltage immunity and the 48 V output has a 63 V backshoot voltage immunity.
These power supplies have 6 kV enhanced surge immunity against grid incoming surges and comply with industry and regulatory standards.
These power supplies have a power ascension capability to meet the load demand for a short time to exceed the rated output power. For example, the high-power RACPRO1-T960/24 power supply can increase the power to 150% for 6 seconds (s), thus avoiding many outages due to transient load conditions.
Another user-friendly feature of the 480 W and 960 W RACPRO1 power supplies is the use of simple vertically arranged LED strips (Figure 3) to indicate the actual output power of the power supply as a percentage of its rated output power.