Was this email forwarded to you? If you like what you read, become a subscriber here.



 

Have a question about electrical safety? Eaton experts are just an e-mail away! Submit your question here and receive feedback from Eaton’s electrical specialists within 48 hours.

Ask the Expert

Interactive Media:

Arc Flash Prevention Launch Tool

Events:

2009 Arc Flash Seminars

Look for an October webinar announcement coming soon.

Links:

Fundamentals of Electricity

AC and DC, What's the Difference?

Did You Know?

DC power is used in the following applications:

• Telecom

• Data centers

• Solar

• Wind

• Fuel cells

• Transportation

Awards

Eaton’s David Loucks was awarded the Conference Prize Paper by IEEE Pulp & Paper Industry Committee for his paper entitled, “Calculating Incident Energy Released with Varying Ground Fault Magnitudes on Solidly Grounded Systems.”



  
 

IN THIS ISSUE

DC vs. AC

Solution Highlight

Did You Know?

Interactive Media

Events

Ask the Expert

       
   

 
   


DC vs. AC theory

While direct current (DC) circuits and systems are already commonly found within variable frequency drives, some types of crane control, certain CNC systems and machine tools, motion-control systems, UPS systems and utility power transmission systems, its overall use has been steadily increasing. This is due to the increasingly common use of alternative energy sources, such as solar photovoltaic (PV) systems, fuel cells, microturbines and emerging energy storage systems. Each of these systems relies on DC power subsystems.

DC power is different from alternating current (AC) power, because unlike AC, where the current passes through zero every half cycle, with DC you must do more to stretch out and cool the DC arc path or the arc won’t extinguish—making DC power harder to break, and with DC, it is more difficult to interrupt an arc.

To learn about the basic theories of DC vs. AC, you can take Eaton’s online training classes. The two links below provide more detail on basic theories of AC and DC power.

Solution highlight—Eaton DC molded case circuit breakers

Eaton’s DC molded case circuit breakers are UL® listed for use in general DC circuits and ungrounded battery supply circuits of UPS systems providing continuous, reliable AC power to computer-controlled applications, such as financial transactions and telecommunications.

Click here to read more.

Ask the Expert

Do you have a question about electrical safety? Eaton experts are just an e-mail away! Submit your question here and receive feedback from Eaton’s electrical specialists within 48 hours.

Q: What set of conditions determine the use of catagory 2 versus catagory 2*

A: NFPA 70E Article 130.3(B)(2) specifies that absent an incident energy analysis (arc flash study), "the requirements of 130.7(C)(9), 130.7(C)(10) and 130.7(C)(11) shall be permitted to be used for the selection and use of personal and other protective equipment."

The PPE requirements listed in 130.7(C)(10) are divided by type of equipment and task performed. You will notice that some of those tasks will call for Category 2* (higher level of neck and back of head protection).