The mechanical stability of the leading wire is critical to the safe, reliable and long-term operation of photovoltaic modules. Its failure may lead to problems such as degradation of electrical performance, moisture intrusion, leakage and fire. The Robustness of Termination Test can determine whether the power connection of the photovoltaic module can support the mechanical loads such as stretching and bending that may occur during the installation process. The Robustness of Termination Tester from Millennial Solar simulates the cable pulling that photovoltaic modules may be subjected to during transportation and installation, and uses a certain mass of pressure and torque to judge the tensile and torsional performance of the leading wire.

IEC61215 standard MQT14 Robustness of terminations

IEC61215 standard MQT14 Robustness of terminations, according to the test process of IEC 61215 standard, 2h to 4h after the humidity freezing test (MQT 12), Robustness of terminations (MQT14) needs to be tested to determine whether the PV module power connection can support mechanical loads such as tension and bending.

Tensile test: 40N force is gradually applied for (10±1)s (according to IEC 60068-2-21), do not pull hard, perpendicular to the installation surface. The tension is applied to the center of the junction box.

Bending test: 40N force is gradually applied for (10±1)s (according to IEC 60068-2-21), each direction should be parallel to the installation surface and parallel to the edge of the module, and change by 90°.

(a) Tensile test (b) Bending test

The Robustness of terminations Test is designed to ensure that the power cables of PV modules can withstand mechanical loads, thereby ensuring the reliability of the modules during use. After this test, it is necessary to repeat the tests MQT 01 and MQT 15 for final measurements. In the terminal strength test, a force of 40N is gradually applied for (10±1)s. The test steps are carried out according to the IEC 60068-2-21 standard. The following is a specific analysis of this standard.

IEC 60068-2-21 Strength of the leading wire and integral mounting parts

Refer to IEC 60068-2-21 to verify the stresses to which the leading wire or the integral mounting may be subjected during normal assembly or operation.

a. Linear lead-out terminal

Pull force F_p applied to an axial leaded specimen

For insulated lead-out terminals, the insulation layer should be stripped at the load-applied location.

For stranded wire lead-out terminals, the stranded wires should be mechanically connected together at the load-applied location before the load is applied (e.g., by soldering or knotting)

b. The value of the tension applied to other types of lead-out terminals (stick-shaped lead-out terminals, bolts, screws, joints, etc.) should be specified in the relevant specifications.

Pull force F_p applied to a radial leaded specimen

Torque test

Determine the ability of the leading wire and the connection between the leading wire and the main body of the test sample to withstand torque during normal assembly or disassembly. Each lead-out terminal is bent 90° at a distance of 6mm~6.5mm from the lead-out point, and the curvature radius of the bend should be about 0.75mm, as shown in the figure.

Torque test

Clamp the free end of the lead-out terminal at 1.2 mm ± 0.4 mm from the bend (as shown in the figure), and then rotate the test sample body or fixture around the original axis of the lead-out terminal at a speed of 1 rotation every 5 seconds. The continuous rotation should be performed alternately in opposite directions.

Torque test - method of twisting the terminal

The following methods and levels are used for testing:

Method 1: The main body of the test sample is clamped, Level 1: 360° three turns, Level 2: 180° two turns

Method 2: Both lead ends are clamped, Level 2: 180° two turns

(Method 2 is mainly used for test samples whose main body is not suitable for clamping and have the same axial lead ends at each end)

Method for twisting the lead-out terminal on a test sample where the main body is not easily clamped

Bending test

Verify the ability of the leading wire and the connection to the test sample body to withstand bending forces during normal assembly and operation. Fix the test sample body so that the leading wire is in the normal use position of the test sample, with the axial direction of the leading wire in the vertical direction, and then hang a weight to apply bending force at the end of the leading wire of the test sample. Tilt the test sample body in the vertical plane by approximately 90° and then return it to its original position.

The bending force values are as follows:

The IEC 60068 standard specifies a series of rigorous test methods to verify the stability of the lead-out terminals and mounting devices under various conditions such as tension, torsion, bending, etc., to ensure that they can withstand the stress that may be encountered during normal assembly, operation and use. The test samples are finally required to undergo visual inspection and electrical and mechanical performance tests.

Junction box and wire fixing test

The junction box separated from the assembly needs to be tested according to the IEC 62790 standard. The specific device and method should meet the following requirements: crimp connection; insulation displacement connection; press-fit connection; insulation piercing connection; screwless clamping device; screw-type clamp; flat, quick-connect terminal; welding connection (according to IEC 60352, 60998, 60999, etc.) After connecting according to the relevant requirements, the following tests need to be performed to verify compliance.

Junction box connection method test:

According to the test sequence, it needs to be carried out after the insulation strength test, as shown in the figure, using a DC current to measure the contact resistance between the external cable and the junction box. The voltage drop should be measured and the contact resistance calculated. These measured values should be listed as reference resistance and shall not exceed 5mΩ. After completing the thermal cycle and subsequent dielectric strength test, the contact resistance measurement should be repeated as described above. The measured value shall not exceed 150% of the reference resistance.

Voltage drop measurement

Robustness of Termination Tester

E-mail: market@millennialsolar.com

Robustness of Termination Tester is a test system designed and developed according to the MQT14 clause of the IEC61215 standard. It is used to verify whether the connection between the leading wire and the photovoltaic module can withstand the forces during normal installation and operation. The test machine is divided into three products: tension tester, torque tester, and adhesion tester.

Torsion test: servo motor applies force; automatic display of torque and angle

Tension test: motor provides power source; weight 30N

Adhesion test: 40N is applied to the center of the box; holding time 10±1s

Robustness of Termination Test determines whether the power connection of the photovoltaic module can support mechanical loads such as stretching and bending, and ensures the reliability of the photovoltaic module during use. Millennial Robustness of Termination Tester ME-PV-RT simulates the situation in which the leading wire of a photovoltaic module is accidentally or intentionally pulled during installation. The equipment applies a certain mass of weight to the leading wire and pulls it back and forth to judge the tensile performance of the leading wire. The equipment uses a motor to apply a certain torque to the leading wire to judge the torque resistance of the leading wire.