Structured Wiring for Photovoltaic Systems

Junction boxes with IP65 protection class are available for both module technologies – silicon modules (monocrystalline and polycrystalline) as well as thin film modules. Junction boxes are installed on the back of the PV modules. They have to primarily conduct the direct current generated by the module to the outside via contact terminals. The junction box comprises, with silicon wafer based modules, one or more voltage-controlled bypass diodes depending on the application. There is one bypass diode at most in the junction box for thin film modules. If one module fails due to shadowing or soiling, for instance, the bypass diodes will ensure that the current is conducted around the affected cell areas.

One feature of the Yamaichi junction box, also called J-Box, is the use of SMD diodes instead of regular radial diodes. SMD diodes have a lower thermal resistance than radial diodes. The thermal resistance of radial diodes is usually about 4 K/W. The SMD diode used by Yamaichi has a thermal resistance of only 1.5 K/W. Therefore an SMD diode will heat up considerably less compared to a conventional radial diode. Higher current resistance, less thermal load and thus also less power loss are the advantages for the user.

Pre-assembled connectors optionally with or without interlock
Cables conduct the current from the junction box with overmoulded connectors. Several modules can be wired up in a row this way. Pre-assembled connectors ensure greater convenience and higher functional safety. They are completely overmoulded and can be mated immediately. Sealing elements are already undetachably installed in the connector. Different cable conductor cross sections from 1.5 mm² up to 6 mm² can be ordered depending on performance requirements. Protection class IP68 is achieved reliably.

Due to the high system voltage of up to 1,000 volt in photovoltaic systems at a direct current of 20 A there is a danger to life from the electric arc discharge during separation under load. To prevent inadvertent separation the connectors may only be able to be separated through high pull-out forces. According to the TÜV standard VDE 126-3 this must be at least 50N if the connector does not have an interlock. The UL standard even stipulates pull-out forces of more than 20 pound (complies with approx. 70 Newton) for unlockable connectors.

Inadvertent pulling out of the contact is prevented for Y-SOL3 plugs (3 mm contact diameter) through high pull-out forces of more than 70N. The Y-SOL4 (4 mm contact diameter) connector has an interlock which is realised with lateral catches. Once plugged in, the connector can be purposely opened only with a tool (e.g. screwdriver).

Resistant material and electrical characteristics
All components are designed for temperatures from -40°C to +110°C. Synthetic polyester materials such as e.g. polycarbonate prevail for the junction boxes. The tightness of the box is achieved with a seal that is undetachably injected into the lid. TPE materials are used for the plastic parts of the connectors.

The contact conversion resistances have values lower than
5 mOhm per connection. Secure bonding is achieved with spring cage contacts in which the ribs surround the contact pin at several contact points. High-performance copper alloys are used as materials.

The six advantages of the Y-Sol® series at a glance:
• Junction boxes are available for both module types: silicon modules and thin film modules.
• Substantially lower heat generation of the junction boxes through the use of SMD bypass diodes instead of regular radial diodes. This results in higher power loading capacity and lower power loss.
• The connectors that are suitable for both module types,
Y-SOL3 and Y-SOL4, are completely overmoulded.
• High pull-out forces, or in the case of the Y-SOL4 an interlock that cannot be loosened without tools, prevent incorrect loosening of the connector under load.
• First available power connector for performances of up to
30 A by Yamaichi Electronics.
• Development and production both take place exclusively in Germany. This allows the development of future products together and in close cooperation with module manufacturers and users.