The Automated Warehouse: A RECOM Story

RECOM recently partnered with a customer to develop a power solution for an automated warehouse application. The client’s core expertise is in high-precision mechatronic solutions and complex software for the storage and handling of goods. To minimize development costs and shrink time-to-market (TTM), their design incorporates off-the-shelf industrial components wherever possible for electronic blocks such as motor drives, sensors, controllers, CPUs, cameras, lasers, interfaces, and wireless communication systems. The combination of high-speed movement and industrial components results in significant shock and vibration stress on the electronics.

Efficient power utilization throughout these systems helps logistics companies provide reliable and rapid service. However, the unique requirements of this type of application make it difficult to find any standard power supply solution. For efficient operation and 24/7 availability, the transport vehicles ride on rails and experience fast acceleration and deceleration.

An additional challenge comes from harsh temperature conditions in a warehouse; temperatures can range from -20°C or lower in cool houses up to over 50°C in hot regions. For safe operation without special isolation protection, the rail is limited to a maximum voltage of 60V. A higher voltage could endanger personnel by generating enough current to cause respiratory arrest or ventricular fibrillation. The rail has a resistance which, although small, is not zero; the DC voltage available to a transport vehicle therefore varies depending on its distance from the main supply and the current it draws. The rail voltage is generated by a high-power, industry-standard, three-phase DIN rail power supply with the output trimmed up to 60V to compensate for large voltage drops on the long rails.

The power for the motors comes directly from the rail. The high power drawn by the motors, and therefore the high currents on the long rails, causes significant voltage drops and ground shifts. In addition, there can be intermittent contact between rails, wheels, or sliding contacts, which can result in voltage dropouts or transients, which are buffered by capacitors. Standard 24V IN industrial equipment is used to minimize cost, so the transport unit's power supply must be able to work across the wide input voltage range supplied by the rails. Total power required by the electronics is 200W.

Due to the unique power requirements, the customer had previously used a complex, discrete, custom design from an external supplier. For the new design, however, the customer was looking for a simpler solution with fewer components and a lower non-recurring engineering (NRE) cost. RECOM suggested an off-the-shelf solution from our large catalog and worked closely with the customer from the early concept stage to the final design.

Engaging with RECOM early in the design process allowed the customer to minimize NRE costs by focusing their efforts on what they do best — the mechanical and electrical design. This way, the customer was able to avoid any redesigns, setbacks, or unexpected surprises normally associated with discrete custom designs.

Figure 2 above shows the blocks powered by the 24V system bus. The harsh electrical environment with its widely varying input voltage, voltage transients, and ground shifts requires an isolated DC/DC converter. RECOM’s solution uses the RPA200H-11024SRUW/P at the heart of the onboard power delivery system. This DC/DC converter delivers an output voltage of 24V DC over an input voltage range of 16.5V to 140VDC. The ultra-wide input range can easily cover the widely varying supply voltage on the rail and handles the expected undervoltages and overvoltages.

The DC/DC converter is a member of the RPA200H series half-brick DC/DC converter family that is designed for the demanding railway industry. Power supplies in automated warehouse vehicles and power supplies for railway rolling stock must meet many of the same challenges: extended lifetime operation in an environment that includes temperature extremes, high levels of shock and vibration, and voltage transients. And, of course, they both run on rails.

The RPA200H-11024SRUW/P has a consistently high efficiency over the entire input voltage range and comes with a metal baseplate to enable a wide operating temperature range from -40°C to +93.5°C when baseplate cooled. The case is fitted with threaded inserts to allow secure mounting to the PCB or bulkhead for use in high shock and vibration environments. The converter is certified to UL/IEC/EN60950 and comes with a three-year warranty.

RECOM helped in other ways, too. The RPA200H-11024SRUW/P datasheet already has a fully-validated EMI filter solution that meets the stringent EN 50121-3-2 railway standard; RECOM supported the design by offering to make measurements of the total solution in RECOM’s EMI lab for the customer.

Another big advantage for the customer was that the previous discrete design had hundreds of different components, including magnetics, that could be difficult to source; the RECOM solution simplified sourcing down to one converter module plus a few components for the filter.