Route Vehicles: Designing for High Voltages and High Temperatures
Route or fleet vehicles operate near continuously under harsh environment conditions. As electrification expands in this market, it’s critical that connectors can endure the influence of high voltages as well as the rigors of the road.
Commercial vehicles operate in uncontrolled environments, subject to heat, moisture, vibration, and dust. For fleet or route vehicles, such as city buses and medium-duty trucks, this is especially true. Route vehicles drive predefined routes each day, operate in all kinds of weather, and navigate a wide array of road conditions. Buses traverse degraded city streets, experiencing extensive vibration on a near-continual basis.
A further design challenge involves projecting and addressing the impact of climate change. Longer, hotter summers, colder winters, and extreme weather patterns such as hurricanes, days of extended rain, and ongoing icy conditions can punish route vehicles, which run on extended schedules and may be stored outdoors.
This is especially true with electrified vehicles. City buses have become increasingly electrified, as cities, states, and nations pass lower or zero-emissions requirements to reduce pollution in compressed urban environments. In the United States, the average transit bus travels 130 miles a day or 34,053 miles a year so ensuring reliable performance is critical.
Now, route vehicles are meeting the twin challenge of harsh environmental conditions and the industry’s drive to high voltage. Higher voltages increase the efficiency of power transfer within the vehicle, which is required not only for the drive train of electric vehicles, but also to handle the increasing power demands of auxiliary equipment and automation features such as advanced driver assistance systems (ADAS). The combination of increasing parasitic loads from more complex electronic systems, as well as extreme heat and cold, drain battery power.
Components Play a Vital Role in Delivering Exceptional Performance
What happens when these high-power electric route vehicles experience constant use, shock, vibration, high temperatures, and humidity? Components take a beating and performance can suffer. Vehicle components, such as connectors, contactor switches, and cable harnesses, may fail if not hardened for ongoing rugged use that can exceed even rigorous military operating conditions.
Common performance issues occur when original equipment manufacturers (OEMs) specify lower-cost parts to save $1 to $3 per part in volume purchase orders. If lower-grade parts fail during operation, bus owners and operators lose $448 to $760 a day in vehicle repairs, driver compensation, lost productivity, and more. OEMs lose too, by harm to their brand reputation for quality and reliability.
Consider the following examples:
- Foot switches can fail if not built to withstand the constant vibration they experience on city streets.
- Switch and relay assemblies, such as those used to turn air conditioning off and on, can fail and take buses out of commission.
- Cable harnesses require greater insulation in high-voltage environments of up to 800 volts that they didn’t experience at 12 to 24 volts, or they can contribute to battery fires.
- Connector seals must be designed to withstand vibration and moisture, carry up to 800 volts without arcing, snap together easily, and maintain their hold in rugged environmental conditions. If they are poorly constructed or suboptimal material selection has occurred, they can short out over time, wear out faster, or corrode.
Any or all of these conditions can sideline a bus for hours or days, costing owners and operators thousands of dollars. Consequently, it it is critical to specify components for the harsh environmental conditions route vehicle applications experience.
Manufacturers can provide OEMs with guidance on route vehicle system performance, providing design expertise for component selection and assembly, and delivering performance guarantees based on tests conducted on components used in real-life operating environments.
As electric buses and other fleets with high-voltage systems expand around the world, connectors designed to withstand the unique conditions these vehicles face will provide owners and operators with the flawless performance they expect and deserve.
For more information, please visit www.te.com/ICT
By Kissling product GmbH, TE Connectivity