Juergen Schoenauer at Omron Electronics Components Europe explores how recent relay innovations are simplifying electric vehicle design
With the global expansion of the market for environmentally friendly clean energy vehicles such as hybrid and fuel-cell cars, there is, a quickly growing demand for mileage extension and new high-capacity battery DC load control technologies. Clean energy car manufacturers are asking for greater circuit design flexibility and components that enable downsizing and weight reduction of on-board electricals
Innovations in high power DC relay design are helping reduce the size and weight of these components, and also simplifying their integration by making them non-polarized. For example, Omron Electronic Components has developed a non polarized contact circuit (contact terminal) that is said to contribute not only to device downsizing and weight-reduction, but also to simplifying mounting.
One of the first relays from the company to feature this technology is the G9EN, a high capacity DC power relay aimed at hybrid and fuel cell cars and other electric vehicles. This relay is also suitable for other DC power applications in renewable energy and industrial systems.
It is half the size (28 by 40 by 50mm) and weights (140g) of the company’s previous comparable relays; achieved using newly developed sealing technologies and new magnetic control methods.
This new relay also features a non-polarized contact circuit, which not only helps make it smaller and lighter, but also simplifies the wiring and mounting in vehicles and other systems.
DC power relays enclose pressurised gas, which hinders arc formation by providing cooling. Typically, a ceramic housing is used to keep the pressurised gas sealed in, but the company has achieved down-sizing and weight reduction of the relay body by changing the ceramic sealing construction from a conventional box-shaped ceramic case to a combination of ceramic plating and metal casing (figure 1).
This makes it possible to maintain or increase the interior volume of the airtight space of the main contact circuit (main terminal) structure compared with existing comparable products.
The layout has been designed so that the spacing, and shape of the switching circuit and the permanent magnet circuit, specifically extinguish arcing, which occurs during DC load interruption across narrow contact gaps (figure 2).
This enables high-speed arc interruption regardless of current direction, and means that the main contact circuit (main terminal) is now non-polarized. This has been difficult to achieve with direct-current type relays using arc interruption via magnetic blowout.
This non-polarization means the device is suitable for use in applications requiring two-way current flow. It also means it is not necessary to consider the mounting direction or the orientation of the device, making wiring and mounting much easier, and reducing the risk of incorrect wiring.
A wider applications focus
The new relay is suited to applications such as main relays and pre-charge relays for vehicles with high voltage batteries such as hybrid and electric vehicles and in BDUs (Battery Disconnect Units). It is also likely to see use in associated systems such as chargers, feeders, and accessories for electric vehicles and plug-in hybrid cars.
Many other green and renewable energy applications also require high voltage DC relays, and although this device is designed for hybrid and electric vehicles, it is also ideal for a number of these. For example, it could be used in feeder circuits and condensers for fuel cell and solar power systems and in dc-powered industrial equipment such as elevators, industrial robots and testing devices.
Solar and wind turbine relays
The device is one of a growing family of high power DC relays for green and cleantech applications. The company substantially re-engineered two other relay families specifically to provide the very low power and long term reliability characteristics needed by grid-connected solar PV and wind turbine inverters, charge controllers, battery powered UPS back-up systems and similar applications.
Grid tied solar PV inverters use pairs of monostable grid protection relays whose operation is essential to ensure system and user safety. The key challenge in the design of these relays is that their power consumption has to be extremely low yet they need to operate very quickly when required under hot start conditions.
They also need a very long operating life, as the payback on PV installations can be up to ten years. The company has re-engineered its G7L-PV DPST-NO and G8P SPST-NO range specifically to meet these requirements, with a fast operate time of typically 20ms, long life and a low power coil.
With the G9EN (60A), the company is advancing down-sizing and weight reduction and is also preparing for the release of other advanced new products including a 150A main relay, and an air-break switch pre-charge relay.
Relay manufacturers have a great contribution to make to the introduction of the next generation of lower cost, lighter and cheaper electric vehicles.
Omron Electronics Components Europe
