Skip navigation

Protective devices

New and patented circuit protection innovations are the result of improved manufacturing technologies, which lower costs and increase quality.Protective device manufacturers have gone beyond product innovation to embrace innovations in manufacturing technology. As a result, they now make products of higher quality. The advances in manufacturing processes, equipment, and methodology have also kept

New and patented circuit protection innovations are the result of improved manufacturing technologies, which lower costs and increase quality.

Protective device manufacturers have gone beyond product innovation to embrace innovations in manufacturing technology. As a result, they now make products of higher quality. The advances in manufacturing processes, equipment, and methodology have also kept production costs down. Thus, you pay for less scrap, less work in progress, less warehousing, and fewer lift truck trips across the production floor. You also benefit from the enormous progress the industry has made in office automation. The amount of paperwork to fill an order, the labor costs of processing that paperwork, and the time delays associated with the whole process have dropped precipitously. Further benefits come in the design efforts, with CAD/CAM making significant reductions in design and prototype testing costs, as well as in machine tooling costs and time to market. This allows manufacturers to keep costs down. It also allows them to allocate resources to offer improved products to better meet existing needs and new products to meet new or emerging needs.

Even with the success of these improvements, protective device manufacturers continue to innovate with new product designs. Some of these innovations improve reliability while others improve other qualities. This past year ushered in new improvements, even in user-friendliness. One example is the expanding array of indicating fuses available. This visual aid to troubleshooting can decrease downtime by reducing the need to pull and check individual fuses; instead, the blown one can be located at a glance. In critical applications, this is a design worth considering. The indicator itself gives a definite good or replace indication. Applications include circuits for general-purpose, lighting, motors, transformers, and solenoids.

Fuseholders are available in touch-safe dead front construction and in more sizes now than in the past. Advances in fuseholder technology include indication lights on the body, a remote communications option (to signal to PLCs or other equipment that a particular fuse in a particular location is open), load-side disconnect switches, and lockout/tagout capability. You can retrofit existing fuseholders with fusecovers that protect personnel from exposed terminals and contacts. The retrofit covers are available with indication as an optional feature.

New power distribution monitoring systems have gone from just being passive to active. Now, you can change the trip curve of a power circuit breaker from your PC as well as take various readings. In addition, you can get such power quality parameters as Total Harmonic Distortion and harmonics present.

Motor protection goes even further, with the advent of a fully programmable, microprocessor-controlled motor protection system that allows motors to run at their maximum safe capacity by providing very accurate overload protection. The device communicates with PCs and PLCs to warn users of possible problems. Since 30% of all motor failures are due to thermal overload, which can be predicted, the device closely monitors thermal rise. In fact, it provides a complete thermal image of the motor - then controls that motor accordingly. Thus, an operator won't destroy the motor by, say, overloading the conveyor it drives.

Category Three


These items have appeared over the past year in EC&M's Product News section and received the highest reader response in their category.

Ground fault indication for generators

The GFA 300 is a ground fault (GF) relay designed specifically for generator applications. NEC regulations require GF monitoring for all generator systems over 1000A at 480V. The GFA 300 is able to sense GF current under all conditions. Applications include: 3-pole or 4-pole transfer switches, multiple transfer switches, paralleling generators, and multiple power sources. No CTs are required, just a simple 4-point connection.

The K-Tec

Molded case 800A breaker

The Sentron molded case LMD frame 800A circuit breaker is 20% narrower and 50% lighter than its MD frame counterpart. Offered as a 2- or 3-pole enclosed, separately assembled or interchangeable trip unit breaker. This circuit breaker switch is rated for 500A to 800A applications and is reverse connectable using either copper or aluminum wiring. The units are available in instantaneous only and thermal magnetic versions.

Siemens Energy & Automation

Minicircuit breaker panel

Free standing panels, only 8 1/2 in. square, have 12 to 42 branch breakers feeding built-in wiring devices. Available in single- or 3-phase for feeders to 225A at 240V. They are factory-wired and tested, easy to modify, and only 11 in. tall (12 poles).


Ground fault circuit breaker

This 2-pole 50A ground fault circuit breaker is vailable in both plug-in and bolt-on versions. The breaker is designed for applications at 120/240VAC and will automatically trip when it senses ground faults at a predetermined level. The plug-in version is available as a people protector, sensing ground faults of 5mA.

Challenger Electrical Equipment

Medium-voltage fuses

The Powr-Gard product line includes medium voltage fuses. These E-rated fuses, for transformer and feeder protection, have been expanded with more than 100 new styles. Designed for the voltage range of 2400 to 25,500 VAC, these fuses are not intended to provide overload protection, but are to be used as fault protection devices.


Indicating fuse

The new 313-ID Indicating 3AG Fuse makes finding a blown glass fuse simple - the glass tube turns brown when the fuse is blown. Provides cost-effective circuit protection. Available in 1/2, 1, 1 1/2, 2, 3, 4, 5, 6 1/4, 7, and 8A ratings at 250V and 10A at 32V.


Category Three


Transformer management relay

The SR 745 high-speed numerical relay combines percent differential, overcurrent, frequency, and over-excitation protection with monitoring of harmonics, THD, harmonic derating factor, and tap position.

GE Multilin

Explosionproof breakers

These explosionproof circuit breakers with enclosures are UL-classified for Class I and II, Groups B, C, and D (NEMA 4X, 7, and 9). Features a padlockable handle mechanism, stainless-steel captive quick-thread cover bolts, and a NEMA 4X O-ring for outdoor applications.

Akron Electric

Mini circuit breakers

Thermal-magnetic miniature molded case circuit breakers provide supplemental overload and short-circuit protection. Compact in size (90 mm long, 68 mm high, 18 mm per pole wide), they offer current limiting design, DIN rail mounting, choice of instantaneous trip characteristics, and blow-out magnet.

GE Electrical Distribution & Control

Power monitor

The MultiComm C meter lowers installation costs with a direct connect feature for power systems up to 480V L-L. Three models are available: 3-wire, 480V L-L, AC nominal, 0 to 540V range; 4-wire, 277V L-N, AC nominal, 0 to 375V range; and 3-wire, 240/208V L-L, AC nominal 0 to 300V range.


Indicating fuses

FLNR-ID and FLSR-ID Indicator Fuses provide power fuse indication in all RK5 applications in any overcurrent or short-circuit situation. The fuses are dual-element, time-delay Class RK5 fuses providing UL-listed protection for 250VAC or 600VAC circuits.


Power monitoring relay

The S7-I/O relay enables the access system to monitor and control power system components that do not have communications capability. Via the system's WinPM software, the device provides remote monitoring and operation of circuit breakers, protective and control relay output, and devices equipped with an auxiliary contact.

Siemens Energy & Automation

Ground fault circuit breakers

These ground fault circuit breakers (GFCBs) operate on single- or 3-phase equipment up to 500V, 60A and come in 2- or 4-pole models. Can be ordered with trip levels of 30mA, 100mA, 300mA, or 500mA, and can work on both pure AC networks or pulsed AC/DC networks.


Circuit breaker retrofit

Medium-voltage air-magnetic circuit breakers can be updated to either [SF.sub.6] or vacuum units, extending life and reducing costly maintenance. Upgrading of MVA and current ratings can be achieved with replacement or conversion units. Circuit breakers are offered from 2.4kV to 34.5kV, 1200A to 3000A, to 1500 MVA.

ASC Industries

Power analyzer

The pa-7 is a 3-phase solid-state paperless recorder combining power quality and power quantity measurement functions. It is a long-term recording volt-ammeter with one cycle response, power recorder, event recorder, harmonic analyzer. It also can capture waveforms. The pa-7 can record for days, weeks, or months.


Hide comments


  • Allowed HTML tags: <em> <strong> <blockquote> <br> <p>

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.