NEMA’s electroindustry May 2010 - (Page 10)
Meeting the Future of Electrical Safety Needs in Plug-in Vehicles
Municipalities are interested in PHEV infrastructure for commercial and public use and to help achieve clean air standards. Charging station manufacturers are providing solutions for residences, workplaces, and public use. The battery and charger size impact the scale of PHEV infrastructure. EVs typically have twice the battery size as PHEVs in order to accommodate longer travel distances. Larger batteries will require faster charging times and higher available current from their associated EVSE. Many electric car drivers will recharge their vehicle at home or work, and if they want to use their vehicles for more than just local trips, they will need to plug them in at commercial locations during their travels. Traditional gasoline cars can generally travel up to 300 miles on a 12-gallon tank of gas, while plug-in electric vehicles travel 100 to 200 miles on a charge. installation process varies—some installations can be less than one week while others may take several months. During some of the early installations, it was found that one installation in southern California was unresolved after 9 months because of local permitting and utility concerns. At this time, the cost and complexity of installation are often unknown. The more the industry can do to reduce cost and complexity, the more the customer will be satisfied. In striving for a streamlined process, the entire installation and EVSE experience creates an optimum opportunity for efficiency. In support of this EV evolution, EVSE has progressed. In the near term (5 to 10 years), plug-in electric passenger cars will use either Level 1 or Level 2 EVSEs (see sidebar). EVSEs have improved in performance and safety over the last several years. The safety-related items designed into both Level 1 and Level 2 EVSEs include personnel protection systems, an interlock circuit, an automatic de-energization circuit, and an enhanced EV-rated cord.
• Level 3, “fast charging,” is for commercial and public applications and is intended to perform similar to a commercial gasoline service station. Level 3 typically uses an offboard charge system serviced by a 480-VAC, threephase circuit. In practice, equipment sizes vary from 60 to 150 kW, with vehicles achieving a 50 percent charge in 10 to 15 minutes. Taken from U.S. Department of Energy Vehicle Technologies Program—Advanced Vehicle Testing Activity, Plug-in Hybrid Electric Vehicle Charging Infrastructure Review; Final Report, Battelle Energy Alliance, Contract No. 58517. (avt.inl.gov/pdf/ phev/phevInfrastructureReport08.pdf) ei
Kenneth Brown, Director of engineering for c&i San Diego, Leviton Manufacturing co., inc.
lectric vehicles and their associated battery technology have progressed at an impressive rate in recent years. The desire to place electric vehicles on the road is driven by many factors, including air quality, dependence on foreign oil, and high gasoline prices. President Barack Obama has called on the U.S. to put one million electric vehicles (EVs) and plug-in hybrids on the road by 2015.
The plug-in electric hybrid vehicle (PHEV) is of significance to many parties beyond consumers and automotive manufacturers. These include utilities, municipalities, charging station manufacturers, and battery manufacturers. Each participant in the value chain has different points of interest. Utilities, for example, are concerned with managing the power needed to service these vehicles. If a community has a cluster of PHEVs, it may impact a local transformer, which in turn could cause an overload. Smart meters create opportunities for utilities to manage and control charging stations. Some utilities are considering electric vehicle supply equipment (EVSE) with a meter built in as an option for monitoring power while charging the vehicle.
Charging Stations Meet Safety Needs
Extensive market research has been completed related to the charging station experience. Setting up an EVSE
the introduction of battery electric vehicles and not the ultimate charging solution. • Level 2 is described as the “primary” and “preferred” method for a battery electric vehicle charger. This method specifies a 240-VAC, single-phase, 40-amp branch circuit, and employs special equipment to provide a higher level of safety required by NEC. Conductive equipment uses “butttype” or pin-and-sleeve type connection and is typically referred to as the EVSE or power control station. Because of the small battery size (typically less than 10 kWh), Level 2 charging may be limited to 15 amp, providing a maximum charge power of 3.3 kW.
Levels of Charging
Three charging levels have been defined by the Electric Power Research Institute and codified in the NEC®. • Level 1 uses a standard 120-VAC, 15-amp (12-amp useable) or 20-amp (16-amp useable) branch circuit that is the lowest common voltage level found in both residential and commercial buildings in the U.S. Because Level 1 only provides a small amount of power (maximum of 1.44 kW) and can result in prolonged charge times, it was only intended to be an entry-level voltage during
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