Danfoss Solar Inverters




"With the same development tools from National Instruments,

we developed a complete solution covering our test needs from PCB testing

to the packing station of the final products."

- Jim  Svenningsen, Danfoss Solar Inverters A/S



The Challenge: Developing a flexible manufacturing test solution for Danfoss Solar Inverters products and printed circuit boards (PCBs) to better enable contract manufacturing worldwide.    

The Solution: Using NI TestStand and LabVIEW software with NI PXI and PCI hardware to develop a standardized test system for testing PCBs and solar inverters.                                       

Inverters for Fast-Growing Solar Markets

Danfoss Solar Inverters develop and manufacture grid-connected inverters converting direct current generated by solar panels into alternating current. We also have products for monitoring the solar energy system to achieve optimal energy output and return on investment.

Our business unit focuses on the fast-growing European solar market. Because of the rapid growth of our business, our goal was to design our manufacturing process to meet the increasing production volume. One of the key areas we wanted to focus on was our test environment.

Looking for a Flexible and Widely Supported Test System

Our old manufacturing and PCB test systems were based on a proprietary test engine that did not support our strategy for expanding our manufacturing operations internationally. We looked for a test environment that could be widely used, including international support and service because we wanted to avoid expensive production interruptions caused by the limited amount of spare parts and service. Furthermore, we set a goal to develop a test architecture that would allow us to test any type of inverter.

After analyzing the off-the-shelf test software and hardware platforms in the market, we decided to standardize our manufacturing test platform on the NI TestStand and LabVIEW software environments. These industry-standard test software tools give us the required flexibility and the ability to outsource test development and service both locally and internationally.

For instrumentation we selected PXI- and PCI-based systems using NI data acquisition (DAQ) and bus interfacing modules. This solution provides an easy way to expand the system when needed while keeping the footprint small. If we need a new test instrument, we just add a new module without having to grow the size of the system.

Working with an National Instruments Alliance Partner for Test System Design

To design the system architecture and develop the entire environment, we worked with NI Alliance Partner CIM Industrial Systems A/S, a leading technology partner with more than 10 years of experience in developing test and measurement solutions based on NI TestStand. The test development capabilities and the return on our investment offered a very good solution.

For our test solution, CIM designed numerous custom NI TestStand step types, making it very easy to add new tests. CIM also customized the NI TestStand process model for our use including custom step types to all instruments and customized error handling. The company also added a Web service interface to retrieve data from our Axapta ERP-system to specify the scope of the test.

Two Hardware Setups

We have two different hardware setups, one for PCB testing and another for final testing of the inverters. The hardware in the PCB tester is built on an NI PXI-1044 14-slot chassis. We used an NI PXI-6704 analog output module to stimulate the inputs of the device under test (DUT) and an NI PXI-6229 multifunction data acquisition (DAQ) device to measure the analog response. We also used NI PXI-8433/2 and PXI-8432/2 modules for RS485 and RS232 communication with the DUT. Two switching modules, the NI PXI-2566 and PXI-2503, are in the system for signal routing and an NI USB-8451 module is used to test the I²C link of the DUT.

In the final test system, we used the same PXI-6229 DAQ modules in PCI format. We measure temperature, voltage, and current signals with the device. The digital channels of the module are used to control door lock relays and read back the door sensor information. Furthermore, the digital outputs also control the relays connecting a DC power supply and the grid to the inverter under test. The analog output channels of the module are used to feed needed voltage and current signals to the DUT and control the output voltages and current limits of the DC power supply. This test phase also requires some RS485 communication; therefore, we applied the PXI-8433/2 module.

The Results of the Test System Standardization Project

In addition to the PCB and final test systems, we use NI TestStand and LabVIEW in our label and packing stations. With the same development tools from NI we developed a complete solution covering our test needs from PCB testing to the packing station of the final products. Today we have a flexible test system in which, even with limited knowledge of NI TestStand and LabVIEW, we can create and edit test sequences for all our products.