104 Chapter 9 Contactors/Relays A contactor is essentially an electromechanical switch, or relay, that will close in order to make the connection and to allow current to flow, or opens to stop the flow of current and voltage ( Figure 1 ). This becomes another important design and safety component of the ESS as it will essentially start or stop the flow of current and voltage to and from the pack. The contactor is considered an electromechanical device as it is a mechanically driven device that makes the electrical connection. DĂŝŶŽŶƚĂĐƚŽƌKƉĞŶʹ EŽƵƌƌĞŶƚ&ůŽǁŝŶŐ DĂŝŶŽŶƚĂĐƚŽƌůŽƐĞĚʹ ƵƌƌĞŶƚ&ůŽǁŝŶŐ Figure 1 Contactor schematic in open and closed positions.
The contactor switch is often enclosed in a hermetically sealed unit filled within a nonconduc- tive gas mixture in order to prevent sparking as the connection is made or broken. Sealing it in a nonconductive gas prevents sparking when the switch closes; additionally, as a sealed unit it can be used in corrosive environments such as the harsh automotive environment without becoming contaminated or corroded. Today there are several major companies that manufacture “off-the-shelf” type contactors for electrified systems.
It is generally preferred to work with a manufacturer of these components in order to select the proper size for your system rather than trying to design one from scratch ( Figure 2 ). Figure 2 Tyco Kilovac 500 A 320VDC EV200 contactor.