Certified Energy Auditor Certification Certified Energy Auditor Motors, Drives, and Compressed Air Questions and Answers 2

Question 1

What is the primary benefit of installing a variable frequency drive (VFD) on a centrifugal fan motor?

Accepted Answer

Energy savings through speed reduction following affinity laws

Answer

Increased motor starting torque

Answer

Elimination of power factor correction needs

Answer

Reduced motor insulation requirements

Question 2

A compressed air system operates at 110 psig but end-use equipment only requires 80 psig. What is the most appropriate energy-saving recommendation?

Accepted Answer

Install a dedicated low-pressure compressor or reduce system pressure with controls

Answer

Replace all pneumatic equipment with electric tools

Answer

Add a larger receiver tank only

Answer

Increase pipe diameter throughout the facility

Question 3

Which motor efficiency standard, mandated by the Energy Independence and Security Act of 2007, applies to most general-purpose motors sold in the United States?

Accepted Answer

NEMA Premium efficiency levels

Answer

NEMA Standard efficiency levels

Answer

IEC IE1 efficiency levels

Answer

EPACT minimum efficiency levels

Question 4

During a compressed air audit, an auditor measures that the compressor is operating at 70% loaded and 30% unloaded time. Which control strategy would most improve part-load efficiency?

Accepted Answer

Variable speed drive control

Answer

Load/unload with a large receiver

Answer

Inlet modulation control

Answer

Start/stop control with no receiver

Question 5

What is the approximate energy cost of compressed air leaks in a typical poorly maintained industrial system?

Accepted Answer

20-30% of total compressor energy

Answer

Less than 5% of total compressor energy

Answer

Exactly 50% of total compressor energy

Answer

Over 75% of total compressor energy

Question 6

When evaluating motor replacement, at what approximate load factor does rewinding a failed standard-efficiency motor become less cost-effective than replacing it with a premium-efficiency motor?

Accepted Answer

Below 75% of rated load

Answer

Below 25% of rated load

Answer

Above 100% of rated load

Answer

At exactly 50% of rated load