The solar junction box works together with the components, solar junction box which requires strong adaptability to the environment. In terms of temperature, the current standard is -40℃~85℃. The junction temperature of the diode will affect the leakage current in its off state. Generally speaking, solar junction box the leakage current will double for every ten degrees of temperature increase. Therefore, solar junction box it is necessary for the diode's rated junction temperature to be higher than the actual junction temperature during use. For example, 2AP1 type germanium diode, solar junction box if the reverse current is 250uA at 25, the temperature will rise to 35, the reverse current will rise to 500uA, and so on, solar junction box at 75, its reverse current has reached 8mA, solar junction box not only lost The unidirectional conductivity will cause the pipe to overheat and damage it.
The actual junction temperature can be measured by the following method: put the component in a 75 degree oven until it is thermally stable, solar junction box pass the actual short-circuit current of the component in the diode, solar junction box and measure the surface temperature of the diode after thermal stability (for example, 1h), according to the following formula Calculate the actual junction temperature: Tj=Tcase + R*U*I, solar junction box where R is the thermal resistance coefficient, given by the diode manufacturer, Tcase is the surface temperature of the diode (measured with a thermocouple), solar junction box and U is the voltage drop across the diode (measured Value), I is the component short-circuit current. The calculated Tj cannot exceed the junction temperature range on the diode data sheet.
The method to test whether the junction temperature of the diode is qualified or not is as follows: the whole component is heated to 75°C, solar junction box and after the reverse current of Isc is applied for 1h, solar junction box the temperature of the bypass diode measured should be lower than its maximum operating temperature. Then increase the incoming reverse current to 1.25 times Isc for 1h, solar junction box and the bypass diode should not fail.