Operator Interfaces, Switches & Relays


Protection for low voltage motors

August 2003 Operator Interfaces, Switches & Relays

NewElec's NJ and NK series motor protection relays offer a cost-effective solution providing protection against motor overloading for both sustained and cyclic overloading conditions. They protect against phase current imbalance and phase loss protection, as well as earth leakage protection with a sensitivity of 250 mA and a trip delay of 100 ms.

The relays' design includes full thermal memory with user-selectable thermal curves in the range 2,5 to 32,5 s. Running stall protection with a factory preset trip threshold of three times motor full load setting is activated as soon as the motor starting sequence is completed. This feature is ideal when protecting mechanical equipment against the effects of impact torque conditions.

As the relays are immune to harmonics, when they are used in conjunction with larger kW motors, nuisance earth leakage trips are eliminated, especially when starting these motors on D.O.L.

Their built-in motor load transducer, a 4 to 20 mA output loop, may be used as an analog input into a controlling PLC. Providing reliable and effective protection for low voltage motors, the relays obviate any further requirements for a separate earth leakage protection relay as well as another transducer. These built-in features are both cost reducing and space saving factors for MCC manufacturers.

The design of the protection relays allows adequate provision for preventing the main contactor from opening on an earth leakage fault current whose magnitude could rise to 'infinity' within a very short time span with possible disastrous results to the main contactor. This is achieved on the NJ model by intelligent assessment of the actual fault current magnitude prior to energising the main trip contact. If the relay assesses that the fault current is exceeding eight times motor full load setting, the trip is blocked to allow for the backup protection to disrupt the supply to the motor. In the case of the NK model a totally separate trip contact is energised. This is designed for connection to the shunt trip mechanism of a backup circuit breaker.

An additional set of four N.O. contacts provide a hard wire link to a remote control room as to the motor status and fault type. Localised, remote and voltage actuated relay reset instructions are included in the package. The relays are designed for door and chassis mounting and can be used over a broad spectrum of current ranges.

For more information contact Luc Dutrieux, NewElec, 012 327 1729, [email protected], www.newelec.co.za



Credit(s)



Share this article:
Share via emailShare via LinkedInPrint this page

Further reading:

High-efficiency switching solutions
Operator Interfaces, Switches & Relays
Becker Mining South Africa has launched a new-generation energy distribution system that has been specially developed to enhance productivity and safety in the challenging conditions of local underground coal mines.

Read more...
Motor protection relay front-end software
NewElec Pretoria Electrical Power & Protection
In the realm of motor protection for critical motor-driven applications, precision and reliability are non-negotiable. That’s where NewElec stands out. Its Motor Protection Relay Front-End software isn’t just another tool, it’s a game-changer that puts control firmly in your hands.

Read more...
World-first solution for platinum miner
ABB South Africa Operator Interfaces, Switches & Relays
When a consulting engineering company approached ABB about a specific problem that its platinum mining client was experiencing at its smelter facility in the North West Province, it was an opportunity for the technology provider to showcase its innovation and adaptability in responding to specific customer requirements.

Read more...
Robust industrial relays
Vepac Electronics Operator Interfaces, Switches & Relays
Industrial RT relays from Vepac are particularly robust and are used for high load control. RT modules can control up to three changeover contacts, with 10 A each. In addition, this product is equipped for safety reasons with manual operation, improved LEDs or free-wheeling diodes.

Read more...
Three-phase motor protection relay
NewElec Pretoria Electrical Power & Protection
The NewCode Dual Ethernet Relay is an ISO 9001:2008-compliant, three-phase motor protection relay, designed and manufactured in South Africa.

Read more...
Pick-to-light device with added flexibility
Turck Banner Southern Africa Operator Interfaces, Switches & Relays
Pick-to-light devices and systems help industrial automation manufacturers reduce the risk of error in the assembly process, ensuring product quality and reducing cost. These devices are also used in kitting and put-to-light operations to ensure high accuracy in fulfilment operations.

Read more...
Accurate, long-lasting relay
NewElec Pretoria Electrical Power & Protection
Newelec’s LA Series is designed to replace the conventional thermal bimetal protection device, and is far more accurate and longer lasting than anything used before.

Read more...
KD Series motor protection relay
NewElec Pretoria Electrical Power & Protection
Newelec’s locally designed, manufactured and distributed KD relay is a comprehensive low-voltage electronic motor protection relay designed for conveyor, compressor, crusher, fan, and pump motor protection.

Read more...
Protection relays – control what you can
Schneider Electric South Africa Operator Interfaces, Switches & Relays
With municipalities’ distribution centres and equipment taking immense strain due to load shedding, maintenance has unfortunately moved down the priority list. The time is now to implement what municipalities can control - protecting and monitoring installed equipment.

Read more...
Programmable multicolour indicator beacons
Turck Banner Southern Africa Operator Interfaces, Switches & Relays
Pro Editor software lets users program the K100 Pro Daylight Visible and K100 Pro Indicator with a variety of alarms, colours and animations.

Read more...