[ Custom UPS ] Rugged Traffic UPS customization Project

Annual Demand – A11H Online UPS 1kVA~2kVA/ 300 units

Backup Power Supply for Traffic Signal Control System.

The customer was developing the traffic signal control system including rugged UPS,  but they did not have sufficient time, human resource, and technical capability to build a Online-UPS by themselves. They were looking for a base unit that they will use but could not find the right one. After months went by, they finally found Sanyo Denki UPS because Sanyo Denki Uninterruptible Power Supply (SANUPS) has been successful in the traffic control equipment market of Japan.  

To begin with, Sanyo Denki provided an Online- COTS UPS(commercial off the shelf), and the customer selected only necessary print circuit boards (PCB) to integrate to their chassis to meet DOT’s (Department of Traffic) requirement and standard as well as NEMA (National Electrical Manufacturers Association) standard.

One of the challenges that we faced was to meet unique NEMA’s requirement that regulates a permanent input voltage wider than UL. (NOT including temporal input voltage range that is often displayed on the product catalog) whereas our COTS unit’s permanent input voltage range has initially been narrower. Please see the charts shown below about operation voltage change in detail.  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Create Synergy by Sharing Technology and Know-How. 

The project’s objective is not only achieving the required specification but also cost-effectiveness and schedule. We thoroughly cooperated with the customer with a higher level of technical support including modifying the firmware, providing schematics, and component thermal performance simulator based on the non-disclosure agreement. The customer brought their sheet metal construction skill and know-how in the traffic industry.   

 

Challenges Summary

1. Permanent Input Range
2. NEMA, DOT, UL1778 Certification
3. Thermal Performance Problem

 

Our Solution

1: Solving a problem by gathering specialist from each section.

Our COTS UPS’s input voltage range is design to be as wide as possible to keep the battery life longer (In general, the UPS system has a permanent input voltage range and temporal input voltage range which is usually 1 min). The UPS will have been worked as a battery-mode more often if the input voltage range is narrow. It will result in the internal battery deteriorates quickly. Though we accomplished such a wide input voltage range after many years, the NEMA-standard was demanding more extended permanent input voltage range which set for extremely harsh outdoor environments.    

Widening a permanent voltage range seemed to be very tough at first, but we did not assume it is impossible. First, we started to gather all information needed such as load equipment electric-characteristics and physical environmental conditions. After many investigations and evaluation, we were able to widen the input permanent input voltage range.

 

2: Thermal Optimization for Print Circuit Board/ Heat Spreader Design

SANYO DENKI has a long history of designing a generator and AC power supply. We have a lot of know-how and experience in the product heat design. For example, all SANUPS UPS systems have optimized component deployment and an air deflector in detail on the PCBs to keep the heat as low as possible.

This traffic signal UPS project needed to re-design heat optimization since the air flow inside a metal enclosure became utterly different from our original UPS system which resulted in overheating. So, a multidisciplinary placement optimization methodology for heat generating electronic components was used and forced convection in an enclosure. It revealed the junctions of temperature, wiring density, line length for high-frequency signals, and critical component location. We needed to optimize them simultaneously using the genetic algorithm, adding a cooling fan to increase CFM, and developing a dedicated air deflector.

As a result, we were able to meet the required unit temperature and pass the evaluation tests. Also, the reactor’s specification in the step-down converter met UL1446 criteria.  

 

 

3: Certification

To help the customer to meet and certify their unit to safety standard of NEMA, UL, and DOT’s, we disclosed and shared technical documentation such as schematics and parts list as well as evaluation test results. As a result, the customer was able to obtain all the necessary certification which was the biggest challenge and success in this project.   

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