When trains pass through tunnels, the temperature often undergoes drastic changes. This significant temperature difference may lead to the formation of water droplets, moisture, and humidity, which have unforeseen effects on equipment. To address these issues, all MINMAX power modules are fully encapsulated to effectively resist the impact of external environmental factors. Furthermore, EN 50155 sets forth specifications for the expected performance of electronic devices in such environments. MINMAX's testing standards go beyond those defined by EN 50155, ensuring equivalent or even stricter testing conditions. For detailed information, please consult Table 3.

A. Low Temperature Start-up Test

    To assess whether the product can start up properly at low temperatures, the testing will be conducted according to the low temperature levels specified in Table 1. The test procedure, as depicted in Figure 3, involves checking the functionality at room temperature before gradually lowering the temperature to the specified level. The stabilization period should last at least 2 hours. Subsequently, the equipment will be powered on for operational checks for 1 hour. Once the checks are completed, the equipment will be allowed to return to room temperature and remain at that temperature for 1 hour before undergoing another round of functionality checks upon restarting. Throughout the testing period and thereafter, the equipment can be deemed to have met Performance Standard A if it functions as expected and operates within its specified range.

Figure 3 A. Low Temperature Start-up Test

B. Dry Heat Test

    To evaluate the performance of the product under high-temperature and dry heat conditions, the testing will be conducted using the high-temperature levels specified in Table 1 and the extended temperatures provided in Table 2, taking into account different external conditions. After selecting Cycle A/B/C, the corresponding test procedures are outlined in Figures 4/5/6. The stabilization period during the test should last for a minimum of 2 hours. If the equipment operates as expected and within its specified range both during and after the testing period, it can be deemed to have met Performance Standard A.

Figure 4. Dry Heat Test - Cycle A

Figure 5 Dry Heat Test - Cycle B

Figure 6 Dry Heat Test - Cycle C

C. Low Temperature Storage Test

    To assess the product's ability to withstand low-temperature storage environments, the product will be placed in a test chamber without any power supply. The test temperature should be set to -40℃ and maintained for at least 16 hours. After returning to room temperature, functional verification will be performed. If the product operates normally within its specified range, it can be deemed to have met Performance Standard A.

D. Cyclic Damp Heat Test

    The purpose of this test is to assess the product's ability to withstand variations in operating temperature and humidity. The test conditions are as follows:

• Temperature : +25℃ & +55℃
• Number of cycles : 2 cycles
• Duration : 2 x 24 hours

If the equipment operates as expected and within its specified range throughout the testing period and thereafter, it can be deemed to have met Performance Standard A.

Figure 7 Cyclic Damp Heat Test - Start of the 24-hour cycles for the first and second time

Figure 8 Cyclic Damp Heat Test - End of the second cycle and recovery period

Figure 9 Full encapsulation potting aids in the converter's resistance to external environmental factors

EN 50155:2017 Mechanical Testing

    In the operation of high-speed trains, all equipment is subjected to continuous vibration, particularly as the speed continues to increase with technological advancements. However, along with these advancements come risks. Therefore, ensuring that equipment can withstand intense impact, vibration, and collisions while maintaining stable output or normal operation is a crucial concern for equipment manufacturers.

    The EN 50155 certification explicitly states that the railway-grade DC-to-DC power converters installed on vehicles must meet the vibration and shock testing requirements of EN 61373. Therefore, strict control must implemented during the manufacturing process to ensure consistency in performance. MINMAX's railway-certified DC-to-DC power converters are specifically designed to meet high-impact and high-vibration tolerance, as well as to ensure stability and minimize the occurrence of faults during long-term operation, as per the EN 61373 vibration and shock standards.

Table 4 – Mechanical Testing

A. Functional Random Vibration Test

    First, we select the installation position of the testing equipment, which is divided into Body Mounting Class A, Body Mounting Class B, Bogie Mounting, and Axle Mounting. The equipment is then tested according to the related root mean square (RMS) values and frequency ranges given in Table 5. In cases where the actual direction of the equipment is uncertain or unknown, the test should be conducted with RMS values in the vertical direction on all three axes. Under the basic testing conditions of Body Mounting Class B, MINMAX increases the "vibration frequency" and "RMS acceleration" parameters to provide customers with greater reliability assurance.

Table 5 - Intensity and Frequency Range of Functional Random Vibration Test

Figure 10 - Horizontal Axis - Illustration of Functional Random Vibration Test Results (MINMAX Enhanced Version)

B. Increased Random Vibration Test

    First, we select the installation position of the testing equipment, which is divided into Body Mounting Class A, Body Mounting Class B, Bogie Mounting, and Axle Mounting. The equipment is then tested according to the related root mean square (RMS) values and frequency ranges given in Table 6. In cases where the actual direction of the equipment is uncertain or unknown, the test should be conducted with RMS values in the vertical direction on all three axes. All types of equipment should undergo a total of 15 hours of testing, with 5 hours of testing conducted separately on each of the three mutually perpendicular axes.

Table 6 - Intensity and Frequency Range of Increased Random Vibration Test

Figure 11 - Horizontal Axis - Illustration of Increased Random Vibration Test Results (MINMAX Enhanced Version)

C. Shock Test

    First, we select the installation position of the testing equipment, which is divided into Body Mounting Class A/B, Bogie Mounting, and Axle Mounting. The tested equipment is subjected to 18 shock impulses, with three tests each performed in the positive and negative directions of the horizontal, vertical, and longitudinal axes. Please refer to Table 7 for the test conditions.

Table 7 - Directions, Intensity, and Duration of the Shock Test

Figure 12 - Positive Horizontal Axis - Shock Test (MINMAX Enhanced Version, 10Grms, 11ms)

Figure 13 - Positive Horizontal Axis - Shock Test (MINMAX Enhanced Version, 100Grms, 6ms)

Figure 14 - Ensuring Long-Term Reliability through Mechanical Testing

EN 45545-2 Fire Protection Testing

The railway transportation industry widely requires that power module materials meet the relevant requirements of fire protection testing specified in EN 45545-2. In the EN 45545-2 standard, different tested materials are classified and defined based on categories R1-R26, which specify the "fire performance parameters and test conditions."

Testing includes:

1. Functional description of fire safety objects
2. Grading and requirement levels for homogeneous materials
3. Internal structural materials

The assessment of fire performance involves the following key parameters:

1. Heat release rate
2. Combustibility
3. Toxicity testing
4. Smoke density

• Different tested materials are evaluated for their fire protection testing level (HL Level) based on the final test results of the "fire performance parameter."
• In railway rolling stock, the fire protection testing level required for the materials used is determined based on the operating environment of the vehicle and the classification of different vehicle categories, as per classification table provided below (Table 4 - Hazard Classification).

Table 4 - Hazard Classification

Application of Railway Vehicles

    The requirements for railway equipment are adjusted based on different railway types, purposes, and installation positions. Please refer to Figure 15 for a further understanding of the typical equipment positions on railway vehicles:

1. Different Types of Railway Vehicles
Different types of railway vehicles, such as urban mass transit, underground transit, high-speed passenger trains, or freight trains, may lead to specific usage conditions.

2. Railway Vehicles with Different Purposes
The intended use of railway vehicles is influenced by geographical destinations and whether they operate underground or above ground. The specific conditions of the equipment may vary, depending on the intended purpose (e.g., the equipment mounting on bogies that are subjected to rapid temperature changes at the tunnel entrances/exits).

3. Equipment Positions on Railway Vehicles
Figure 15 illustrates the typical equipment positions on railway vehicles, such as Position 4 (underneath or on the roof of the vehicle), Position 5 (between vehicles), Position 6 (bogies), and Position 7 (axles), which are subjected to different conditions of use based on their design in different positions. Table 5 provides an overview of the equipment positions and the corresponding requirements.

Table 5 - Examples of Typical Equipment Positions on Railway Vehicles

End of Why is it necessary for a power converter to comply with the EN 50155 railway certification? (Part 2)

Thank you for watching. If you are interested, please refer to the previous episode:"Why is it necessary for a power converter to comply with the EN 50155 railway certification? (Part 1)."

For more information, please click on the following links:

• [MINMAX Railway Certified Products _ Power Solutions]
• [MINMAX Railway Certified Products _ Product Selection Guidebook]
• [MINMAX Railway Certified Product _Product Introduction Video]
• [MINMAX Railway Certified Series _ Quarter Brick_MRZI150 Series]
• [MINMAX Railway Certified Series _ 2" x 1"_MKZI40 Series]
• [MINMAX Railway Certified Series _ DIP-24_MIZI03 Series]