IMPLICANCIAS TERMOMAGNETICOS DE 60 Y 50 hz
ROLANDO CANORIO VASQUEZ
Estimados si pudieran darme luces de las implicancias que pudieran haber, el sistema de Perú es de 60 hz el expediente técnico de la edificación especifica que los termomagnéticos
deben ser de 60 hz, el contratista puso de 50 hz. De paso enviarles un cordial saludo
Gracias por sus comentarios.
Atte.,
Ing Rolando Canorio Vásquez
Pucallpa Peru
omar graterol
Rolando, la mayoria de los Molded Case Circuit Breakers (Termomagneticos), se pueden usar indistintamente en 50 y 60 Hertz segun los ratings publicados por el fabricante, segun catalogo o paper de GE sobre aplicacion de breakers; donde se puede ver que el factor del rating para la seleccion en frecuencias de 50 y 60 Hertz es 1,0; no obstante para otras frecuencias se debe tener mucho cuidado debido a la influencia de la frecuencia en el calentamiento por efecto magnetico del elemento magnetico, lo cual influye en la presicion del disparo termico. A continuacion copio parrafo del paper anexo, donde aclaran este aspecto.
************************** Parrafo Copiado ********************************
System operating frequency also has a major effect on the rating and performance of molded case circuit breakers. Most circuit breakers may be directly applied at their published ratings on 50 or 60 Hertz systems, but molded case circuit breakers should not be applied at other frequencies without the concurrence of the General Electric Company except as described on page 36, “Factor C — Frequency Rating”.
Two separate effects occur at frequencies above 60 Hertz depending on the method of current sensing. In thermal magnetic devices, the bimetal, which provides overload protection, responds accurately to the applied current. However, the instantaneous element, which is a solenoid constructed of copper and steel, becomes hot. This raises the temperature of the breaker, thereby reducing the continuous current rating of the device. The instantaneous trip solenoid becomes hot because of the nature of its construction and materials. In addition to adding heat to the breaker, the instantaneous trip does not respond to current correctly; the higher the frequency, the less accurate the response. At nominal system frequencies less than 50 hertz but above direct current, solid-state trip devices become inoperative due to sensor saturation. Thermal trip devices remain accurate while instantaneous trip solenoids lose accuracy. On direct current systems, solid-state trip units are completely inoperative, thermal trip units calibrate accurately, and instantaneous trip solenoids may or may not be accurate depending on the specific construction technique used. **************************Fin del parrafo Copiado **************************
Saludos,...................Omar Graterol
Ingeniero Electricista
Maracaibo - Zulia - Venezuela
Telf. 58-261-7436648
|