Future Electronics, a global leading distributor of electronic components, announces immediate availability of industrial automation and control protection with the UltraMOV Series from Littelfuse.

Low voltage (12 to 48VDC) circuits are used in a wide variety of applications, including automation control systems (PLCs), industrial control contact relays, and many other system types. Over-voltage transients can damage integrated circuits (ICs) or other sensitive devices, as well as cause interruptions in service or loss of data. They may even pose a threat to equipment users. Transients on these lines are often the result of lightning interference, inductive spikes from power switching, or fast transients from induced power line fluctuations. For example, a relay switching on/off can cause a magnetic transient in the coil inductance, which produces a high voltage spike. To suppress these transients, circuit designers typically incorporate a shunt element that acts as a clamp, such as a varistor.

When compared with other voltage suppression technologies, varistors offer one of the most cost effective ways to protect against high-energy surges. Varistors are voltage dependent, nonlinear devices with electrical behaviour similar to that of back-to-back zener diodes, providing excellent transient suppression performance. One type, the metal oxide varistor (MOV), can dissipate very high levels of transient energy across the entire bulk of the device, so they are often used to suppress high energy transients found in industrial or AC line applications.

To extend the life of the relays used in industrial automation and motor control circuits, circuit designers often use MOVs on the secondary side. The MOVs clamp down transient voltages and prevent arcing during the switching of the relay contacts. The MOV absorbs the arcing energy from the energy released from the magnetic fields of the relay.

Low voltage surge protective device (SPD) modules are often used in industrial applications to provide module-based surge protection of complete systems. These SPDs are typically DIN rail modules. The high surge handling density that the latest MOV designs make possible inside these SPDs can offer significant protection advantages.

For these types of applications and many others, the Littelfuse LV UltraMOV™ series of low voltage, high surge current, radial leaded varistors offers superior surge current ratings, energy handling capabilities, and ability to withstand multiple strikes. Its patented, proprietary formulation provides far greater surge withstanding capability than other technologies on the market today. For example, a 10mm LV UltraMOV series varistor offers a maximum surge current rating that's four times higher than a standard MOV of the same size to protect against high peak surges, including lightning strike interference, electrical fast transients on power lines, and inductive spikes in industrial applications. The higher surge rating also provides for longer life and reliability because there's less degradation of the MOV over its lifetime.

Available in disc sizes from 5 to 20mm, LV UltraMOV series varistors are just half the size of standard MOVs with the same surge capability. For example, circuit designers could replace an ordinary 10mm MOV with a 500A surge rating with a 5mm LV UltraMOV varistor with the same surge rating. Circuit designers who use LV UltraMOV varistors can also reduce their part counts based on the total surge level. These devices' compact design reduces both PCB space requirements and component height, making more room available for higher value functional components. The use of a smaller disc also reduces the weight and cost of the final product.

High operating temperatures are common in industrial settings. When specified with the optional phenolic coating, these varistors can be operated in environments up to +125°C, so they're well suited for use in severe conditions.