Functional safety test system

for photovoltaic applicationsfor inverteron site

Overview
Fully automatic safety test system for solar inverters combining hipot, function testing with automatic adjustment, a running-in station and a customising station for firmware and cover installation.

Industry
Solar industry

Task
Implement test systems to perform initial safety and functional checks, fully automatic adjustment of inverters, burn-in under load before storage, and final customer-specific firmware/cover installation. Ground bond and integrated display checks are performed at end of line.

Solution
The three main steps (hipot, function test including adjustment, and running-in) are integrated into a high-rack system with storage-and-retrieval conveying. Inverters are prewired on adapted workpiece carriers so that contacting in individual test cabins is fully automatic via contact pins. Inverters remain on carriers until final packaging; carriers are recognized and the appropriate test program is selected from a database after one scan during assembly.

Key elements of the solution
Hipot test system
Test between input and output and between input strings up to 6 kV DC.

Function test system with DUT adjustment
Automated firmware installation and automatic adjustment of input and output (voltage, current, power). Real values are measured with power meters and compared with inverter data. Functional and connection tests are included.

Running-in station
Each inverter is operated under load for approx. 1 hour. Power is supplied from DC sources and converted voltage is fed back to the mains. Waste heat is stored in a water tank for building heating. Data are logged regularly. Up to 8 running-in stations can be controlled by one PC. Redundant subsystems increase availability.

Customising system
Final firmware version is installed before delivery; OEM-specific firmware and cover assembly are available.

Ground bond conductor test system
Cover integration and protective earth connection are completed at the end of line. The display integrated in the cover is visually checked. A customising and ground bond test station is positioned before each packaging station.

Benefits

• Low contacting effort: one-time manual connection to workpiece carrier enables fully automatic contacting thereafter.
• Fully automatic adjustment.
• High availability through multiple execution of subsystems.
• Automatic test program selection via database.
• No set-up time thanks to carriers adapted to DUT variants.
• Low personnel costs for testing.
• Easy, intuitive operation for trained personnel.

Technical data (summary)

• 2 hipot test stations (up to 6 kV DC).
• 10 function test stations.
• 43 running-in stations.
• 2 customising stations.
• 2 ground bond conductor test stations.
• Running-in duration: approx. 1 hour per inverter under load.
• Up to 8 running-in stations controllable by a single PC.

Characteristics / technical specifications

• Automatic database-driven test program selection based on scanned DUT linked to workpiece carrier.
• Workpiece carriers with pre-wiring enabling automatic contacting via contact pins.
• Hipot test: up to 6 kV DC between input/output and between input strings.
• Function test: automated firmware installation, automatic measurement and adjustment of voltage, current and power using power meters; functional and connection tests.
• Running-in: inverter operated under load, regenerated power fed back to mains; waste heat stored in water tank for building heating.
• High-rack storage with storage & retrieval conveying system integrated into production flow.
• Customising: final firmware installation and cover assembly prior to packaging; visual check of integrated display and ground bond connection test.
• Design approach: redundancy and multiple instances of subsystems to maximize availability and avoid production stops.