Thermal tripping test equipment for MCBs

High temperatures for safe testing

There are different ways of thermal tests. One test uses the nominal current for about 1 hour (this time can be adjusted) to heat the products. This is done under labor conditions with stable temperature. After this time the current  increases and the devices should trip in a defined time period. There can be defined several steps of rising currents. This test is normally done with 10 products (5, 10 or 12). So when one product is tripping, this needs to be dedicated quickly and the product needs to be bridged. This is done by semiconductors. They are working without noise and wasting.


The tripping time is shown on the screen and the results are stored in a file.
Depending on the products the impedance can variate much. The small values need therefor small currents but quite high voltages. At the higher current devices the situation is opposite the current is high but the voltage can be low. So the generator needs to change the stages. Specially for the range from 0.5 to 2.5 A the voltage needs to be very high. In this range we use a separate unit. We built those equipments with light curtain or doors, depending on the customer. If there is a heating unit integrated, doors need to be installed to regulate the temperature.


A second thermal test is the short time thermal tripping

The devices are tested at the production. The current will be increased to a value that is short under the magnetic tripping level. So the products reach fast the temperature to trip. Normally those times are between 10 and 30 seconds. Similar to the long therm tests used in labor, there are 10 products tested at the same time. But at this equipment the products don´t start at the same time. As soon as one product is place into one cavity it will be contacted and the current will start to run. All stations which are free will be bridged. The time for each cavity is counted separate. Different to the long term test where the contactation needs to be done by defined cable diameters and length, this short time test can be done by direct contacts. The display shows for each product the tripping time as a bar with variable  length and color depending on the situation if the product was in the tolerance or not (green or red).