Quantcast TIME DELAY RATINGS

Share on Google+Share on FacebookShare on LinkedInShare on TwitterShare on DiggShare on Stumble Upon
Custom Search
 
  
 
2-26 TIME DELAY RATINGS Circuit breakers, like fuses, are rated by the amount of time delay. In circuit breakers the ratings are instantaneous, short time delay, and longtime delay. The delay times of circuit breakers can be used to provide for SELECTIVE TRIPPING. Selective tripping is used to cause the circuit breaker closest to the faulty circuit to trip. This will remove power from the faulty circuit without affecting other, nonfaulty circuits. Figure 2-22 should help you understand selective tripping. Figure 2-22.—Use of circuit breakers in a power distribution system. Figure 2-22 shows a power distribution system using circuit breakers for protection. Circuit breaker 1 (CB1) has the entire current for all seven loads through it. CB2 feeds loads 1, 2, 3, and 4 (through CB4, CB5, CB6, and CB7), and CB3 feeds loads 5, 6, and 7 (through CB8, CB9, and CB10). If all the circuit breakers were rated with the same time delay, an overload on load 5 could cause CB1, CB3, and CB8 to trip. This would remove power from all seven loads, even though load 5 was the only circuit with an overload. Selective tripping would have CB1 rated as long time delay, CB2 and CB3 rated as short time delay, and CB4 through CB10 rated as instantaneous. With this arrangement, if load 5 had an overload, only CB8 would trip. CB8 would remove the power from load 5 before CB1 or CB3 could react to the overload. In this way, only load 5 would be affected and the other circuits would continue to operate. PHYSICAL TYPES OF CIRCUIT BREAKERS All the circuit breakers presented so far in this chapter have been physically large, designed to control large amounts of power, and used a type of toggle operating mechanism. Not all circuit breakers are of this type. The circuit breaker in figure 2-23 is physically large and controls large amounts of power; but the operating mechanism is not a toggle. Except for the difference in the operating mechanism, this circuit breaker is identical to the circuit breakers already presented.


Electrical News
The Art Of Electronics 3rd Edition is Almost Here!
Massive news! A new edition of the bible is almost...
eevblog.com
Wi-Fi Alliance Radiates Outward
The Wi-Fi Alliance is one of several industry groups grappling...
eetimes.com
Connected Car: Dramatic Growth Ahead
Market research and IT consultant firm Gartner predicts a dramatic...
eetimes.com
What Drove CES 2015 Innovation? IP and IP Subsystems
How do we manage all those blocks in an age...
eetimes.com
What Drove CES 2015 Innovation? IP and IP Subsystems
How do we manage all those blocks in an age...
eetimes.com
The Problem with Big Data
There is a lot of potential in Big Data, but...
eetimes.com
UMC Boosts Capex to Capture More 28nm Orders
UMC's large capex increase to capture more 28nm orders indicates...
eetimes.com
Moore's Law Cover Human Progress
Can a Moore's-like law be applied to anything? Where there...
eetimes.com
Quantum Entanglement Now On-a-Chip
Uncrackable encryption and quantum computers enabled by tiny 20 micron...
eetimes.com
Patent Law's Global Grey Areas
Patent law has unresolved grey areas when it comes to...
eetimes.com
TSVs to Split More Chips: Re-Integration is the Focus
At the 3D TSV summit, the speakers agreed on one...
eetimes.com
Startup Casts a Better IoT Network
Startup IoT Freeway claims it has a better wireless network...
eetimes.com
Open Office: Your Fart is My Problem
Open offices are the future. What a shame....
eetimes.com
Open Office: Your Fart is My Problem
Open offices are the future. What a shame....
eetimes.com
Configuration Tools Simplify MCU Setup
Graphical tools supporting developers in configuring complex MCU peripheral sets...
eetimes.com
Is Freescale Out of the Woods?
Freescale Semiconductor, burdened by large debt repayments since it was...
eetimes.com
EEVblog #709 – EDC 4601 AC Voltage Standard Teardown
Dave does some performance checks and then tears down a...
eevblog.com
iPhone Dials Up Record Apple Sales
Apple announced record financial results for the first quarter of...
eetimes.com
Fried Cable Sparked EE Profession
The electrical engineering profession was sparked in the late 1800s...
eetimes.com
2014: A Monumental Year for Cyber Attacks
As consumer and industrial IoT adoption rises, so does the...
eetimes.com
 


Privacy Statement - Copyright Information. - Contact Us

comments powered by Disqus

Integrated Publishing, Inc.
9438 US Hwy 19N #311 Port Richey, FL 34668

Phone For Parts Inquiries: (727) 755-3260
Google +