Inverters in Electric Mobility and the Requirements for Connectors
Power Management and Intelligent Power Supply
Battery management systems and power electronics play a key role in electric mobility, as they connect the various components within an electric vehicle. The connectors within the inverters serve as the connection points. They are required to control and transmit signals, data, and high currents reliably, safely, quickly, and without loss, despite the demanding operating conditions. To do this, the connectors must meet certain requirements in terms of temperature resistance, compactness, and flexibility, as well as performance and robustness.
Background: The Shift to E-Mobility
In recent years, the automotive industry has seen a shift toward e-mobility.
This shift is evident in the increased production of electric vehicles (EVs), rising sales figures, and the expansion of the charging infrastructure for electric vehicles. Consumer demand for more sustainable transportation options is growing steadily. Likewise, significant investments have been made in battery technology to achieve advancements in the range, performance, and cost of electric vehicles. Government incentives for EV adoption, automakers’ commitments to phase out the internal combustion engine, and stricter emissions regulations continue to drive the shift toward electric mobility.
As a result, traditional automakers are increasing their production of electric vehicles.
This shift is evident in the increased production of electric vehicles (EVs), rising sales figures, and the expansion of the charging infrastructure for electric vehicles. Consumer demand for more sustainable transportation options is growing steadily. Likewise, significant investments have been made in battery technology to achieve advancements in the range, performance, and cost of electric vehicles. Government incentives for EV adoption, automakers’ commitments to phase out the internal combustion engine, and stricter emissions regulations continue to drive the shift toward electric mobility.
As a result, traditional automakers are increasing their production of electric vehicles.
Inverter in an electric vehicle
Inverters are responsible for intelligent power supply and energy management in electric vehicles. They connect the electric vehicle’s battery to the vehicle’s electrical components and, during charging, to the public power grid. This process requires different voltage levels. Two main
types of inverters are used in electric cars: DC/DC inverters and AC/DC inverters. DC/DC inverters convert the voltage of direct current. AC/DC inverters (converters) convert direct current to alternating current or vice versa. Inverters thus convert electrical energy into the voltage level and form required by the load to ensure optimal performance.
In electric vehicles, inverters thus ensure efficient power transfer between the battery and the electric motor to maximize range. Furthermore, inverters must perform various protective functions to safeguard the electric vehicle and its components against overload, overvoltage, and overheating. Overall, inverters help ensure that the electric vehicle operates safely, efficiently, and reliably while delivering high performance.
types of inverters are used in electric cars: DC/DC inverters and AC/DC inverters. DC/DC inverters convert the voltage of direct current. AC/DC inverters (converters) convert direct current to alternating current or vice versa. Inverters thus convert electrical energy into the voltage level and form required by the load to ensure optimal performance.
In electric vehicles, inverters thus ensure efficient power transfer between the battery and the electric motor to maximize range. Furthermore, inverters must perform various protective functions to safeguard the electric vehicle and its components against overload, overvoltage, and overheating. Overall, inverters help ensure that the electric vehicle operates safely, efficiently, and reliably while delivering high performance.
Inverter Requirements
Inverters must meet a wide range of requirements. These include compatibility, ease of integration, and efficiency. This means that inverters must be compatible with other systems in the electric vehicle, such as the battery, electric motor, and control unit. In addition, inverters must be easy to integrate in order to simplify the assembly of the electric vehicle and save time and costs. Furthermore, high efficiency is essential to enable long ranges. Reliability, cost-effectiveness
, and overload protection must also be ensured. Reliable operation is necessary to guarantee stable performance for safe and uninterrupted driving. Inverters must be affordable to meet the economic requirements of the electric vehicle. Inverters must also be equipped with overload protection to prevent overcurrent and overvoltage conditions and to protect the electric vehicle and its components.
In terms of technical requirements, temperature resistance, compactness, performance, and robustness play a central role. Thus, inverters must:
, and overload protection must also be ensured. Reliable operation is necessary to guarantee stable performance for safe and uninterrupted driving. Inverters must be affordable to meet the economic requirements of the electric vehicle. Inverters must also be equipped with overload protection to prevent overcurrent and overvoltage conditions and to protect the electric vehicle and its components.
In terms of technical requirements, temperature resistance, compactness, performance, and robustness play a central role. Thus, inverters must:
- function reliably across a wide temperature range to be suitable for use
- in a vehicle be compact and lightweight, as any additional weight reduces the range of an electric vehicle
- demonstrate high performance in power and data transmission to meet the needs of the
- electric motor and other systems be resistant to environmental influences, shock and vibration, both during installation and assembly as well as during automated joining and in operation.
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Requirements for connectors in inverters
Inverters connect the various components in the vehicle, such as the battery storage system and the electric motor. To do so, the inverters must meet the requirements listed above in order to transmit data and electrical currents reliably and in real time. The connectors
are responsible for establishing the connection between the circuit boards within the inverters. These connectors must transmit signals, data, and currents reliably, safely, quickly, and without loss despite demanding environmental conditions. Consequently, comparable quality requirements apply to the connectors.
are responsible for establishing the connection between the circuit boards within the inverters. These connectors must transmit signals, data, and currents reliably, safely, quickly, and without loss despite demanding environmental conditions. Consequently, comparable quality requirements apply to the connectors.
Temperature resistance
The materials used in connectors must be able to withstand high temperatures, as required by automotive operating conditions. When selecting the right connector, a wide variety of plastic materials are available for the insulator body. However, LCP (liquid crystal polymers) offers particularly excellent properties in this context. An LCP insulator body offers exceptional dimensional and thermal stability, high rigidity—even in thin-walled components—and a low coefficient of linear thermal expansion. The UL 94 V-0 flammability rating allows for operating temperatures of -55°C to +125°C in connectors with LCP insulating bodies.
Compactness and flexibility
Connectors with a small pitch are ideal for use in inverters because they are space-saving, require minimal installation space on the circuit board, and thus meet the need for compactness. Systems with a pitch of 1.27 mm, 0.8 mm, or 0.5 mm, for example, are used for this purpose. However, connectors should not only be small but also adaptable to a wide variety of requirements. This applies, for example, to the required heights, number of pins, or PCB layouts. With connectors such as the One27 from ept, the wide range of designs allows for the connection of PCBs in parallel, horizontal, or right-angle arrangements, as well as the connection of ribbon cables to the PCB.
The right connector system:
The One27 from ept allows for the seamless adjustment of horizontal PCB spacing from 8 mm up to 20 mm. This is made possible by the connector’s design, which features a 2.4 mm contact overlap. By using a cable connection, tolerances can be compensated for in all directions depending on the application, and PCB spacing can be customized to meet specific requirements.
For more information about the product, click here:
One27 »
The One27 from ept allows for the seamless adjustment of horizontal PCB spacing from 8 mm up to 20 mm. This is made possible by the connector’s design, which features a 2.4 mm contact overlap. By using a cable connection, tolerances can be compensated for in all directions depending on the application, and PCB spacing can be customized to meet specific requirements.
For more information about the product, click here:
One27 »
Performance
Good signal integrity characteristics—which ensure the quality of data transmission from the transmitter to the receiver—and signal protection are essential for use in inverters. This is because the data transmitted via the connector enables the inverter to intelligently transmit data in real time to the connected loads. The quality of data transmission depends on three criteria:
- The impedance profile: As soon as the impedance changes along the transmission path, the signal is reflected, which degrades the quality of the data transmission. Even a change in material or geometry can cause the impedance to fluctuate.
- Insertion loss: This parameter helps determine whether the receiver can clearly identify a signal throughout the entire transmission path. If a typical insertion loss value of -3 dB is used as a criterion for the data rate in the Zero8 connector from ept (SMT connector with a 0.8 mm pitch and ScaleX technology), this results in a transmission speed of at least 16 Gbit/s at 8 GHz.
- Cross-talk during signal transmission: Cross-talk is the unwanted interference of a signal by a signal on another line, whereby a distinction is made between near-end and far-end cross-talk depending on the type of interference. The severity of cross-talk depends largely on the signal and ground assignment.
The signal integrity characteristics of a connector can be significantly improved through EMC (electromagnetic compatibility) protection. Electromagnetic compatibility refers to the ability of a technical device not to be disrupted by intentional or unintentional electrical or electromagnetic effects, nor to disrupt others. Electromagnetic interference in connectors can be reduced through a shielding design. The coupling inductance simulates the connector both as a source of interference and as a sink for interference. The effect of the shielding concept can be clearly seen in the following figure based on the color gradients and the values of the coupling inductance.
By using the shielded Zero8 connector, noise sources and sinks on the printed circuit board can be positioned closer together, and the electrical device can achieve higher performance ratings in the required burst and surge tests.
In addition to signal integrity characteristics, a connector’s current-carrying capacity for power transmission is also a key capability. Current-carrying capacity curves can be used to determine how much current may be passed through a contact at a given ambient temperature without exceeding the component’s maximum allowable temperature limit. The following derating curve illustrates how different current ratings per contact result for the zero8 connector depending on the number of poles and the number of current-carrying contacts.
As shown in the figure, a 12-pin connector (blue curve) achieves a higher current-carrying capacity compared to an 80-pin connector (green curve). This is due to reduced hotspot formation inside connectors with fewer pins: less heat is generated, and it can be distributed more effectively. Heat dissipation improves further when current flows through only a small portion of the contacts (red curve).
As shown in the figure, a 12-pin connector (blue curve) achieves a higher current-carrying capacity compared to an 80-pin connector (green curve). This is due to reduced hotspot formation inside connectors with fewer pins: less heat is generated, and it can be distributed more effectively. Heat dissipation improves further when current flows through only a small portion of the contacts (red curve).
Robustness
In SMT connectors, robustness is demonstrated, for example, by the design of the contact mechanism between the male and female connectors—which features dual contact points—the quality of the contact plating to minimize surface wear, and the solder pads, which must be designed to ensure optimal meniscus formation. During processing and handling, SMT connectors must remain as robust as possible. During mating, insertion chamfers and a generously dimensioned catch area provide high tolerance compensation and ease of handling.
Connectors in an inverter are exposed to high levels of shock and vibration, as they are typically mounted close to the motor. Shock and vibration jeopardize the constant and interference-free contact between the circuit board and the connector, as well as between the connectors themselves. Reliable and durable contact between a connector and the PCB can be achieved, for example, through press-fit technology. The goal of press-fit technology is to achieve the highest possible retention forces between the connector and the PCB. This is because the holding forces determine the mechanical connection, which in turn must withstand shock and vibration. This connection technology is a proven process in which a press-fit pin is pressed into a PCB hole, and through mechanical deformation of the pin, a gas-tight, corrosion-free, low-resistance, and electrically conductive mechanical connection is created, which is also suitable for potting. ept GmbH offers both catalog products and custom solutions utilizing this manufacturing technique.
In this process, the press-fit pin has a larger cross-sectional diameter than the PCB hole diameter. The connector pin is flexible in the press-fit zone to ensure that the PCB is not deformed or damaged by the physical forces during the press-fit process. Deformation is thus limited to the press-fit zone. During the press-fit process, a cold weld forms between the contact pin and the metallized PCB hole, making the connection mechanically robust without subjecting the PCB to thermal stress from a soldering process. This technique is specified in DIN EN 60352-5 and remains reliable even under very high mechanical and thermal stresses, such as vibration, bending, and extreme temperature changes, while withstanding shock loads of up to 200g. Thanks to press-fit technology, the flexilink connector from ept offers distinct quality characteristics:
In this process, the press-fit pin has a larger cross-sectional diameter than the PCB hole diameter. The connector pin is flexible in the press-fit zone to ensure that the PCB is not deformed or damaged by the physical forces during the press-fit process. Deformation is thus limited to the press-fit zone. During the press-fit process, a cold weld forms between the contact pin and the metallized PCB hole, making the connection mechanically robust without subjecting the PCB to thermal stress from a soldering process. This technique is specified in DIN EN 60352-5 and remains reliable even under very high mechanical and thermal stresses, such as vibration, bending, and extreme temperature changes, while withstanding shock loads of up to 200g. Thanks to press-fit technology, the flexilink connector from ept offers distinct quality characteristics:
- Minimal nozzle effect (i.e., deformation of the conductor track)
- Prevents cold solder joints and short circuits caused by solder bridges.
- High strength and robustness combined with excellent spring properties.
- Process-reliable workability thanks to optimal adaptation to the processing technology.
- Reliable reproducibility in manufacturing due to stamped shaping.
- Meets the highest requirements of leading manufacturers in automotive electronics.
- Maximum reliability and failure safety proven billions of times over.
Would you like to learn more about press-fit technology?
For a detailed overview of the fundamentals of press-fit technology, we’d be happy to send you our free white paper: Request
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For a detailed overview of the fundamentals of press-fit technology, we’d be happy to send you our free white paper: Request
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