Certified Energy Auditor Certification Certified Energy Auditor Motors, Drives, and Compressed Air Questions and Answers 3

Question 1

What does the term 'specific power' measure in a compressed air system audit?

Accepted Answer

Energy input per unit of air output (kW per 100 cfm)

Answer

Maximum pressure the compressor can achieve

Answer

Total horsepower of all installed compressors

Answer

Ratio of receiver tank volume to system demand

Question 2

A synchronous motor operating at leading power factor provides which additional benefit to the electrical system?

Accepted Answer

Power factor correction, reducing reactive power demand charges

Answer

Higher starting torque than induction motors

Answer

Lower initial purchase cost than induction motors

Answer

Elimination of the need for a motor starter

Question 3

In a compressed air system, what is the recommended maximum pressure drop between the compressor discharge and the point of use?

Accepted Answer

10% of discharge pressure or less

Answer

25% of discharge pressure

Answer

No more than 1 psi total

Answer

50% of discharge pressure

Question 4

Which type of drive mechanism typically offers the highest efficiency for constant-speed motor applications?

Accepted Answer

Direct coupling

Answer

V-belt drive

Answer

Flat belt drive

Answer

Chain drive

Question 5

An energy auditor discovers a 100-hp motor running a constant-torque conveyor at 60% speed using a throttling damper. What is the recommended retrofit?

Accepted Answer

Install a VFD and remove the damper

Answer

Add a soft starter to reduce inrush current

Answer

Replace with a two-speed motor

Answer

Install a larger motor to improve efficiency

Question 6

What is the primary reason compressed air is considered one of the most expensive utilities in industrial facilities?

Accepted Answer

Compressors convert only about 10-15% of electrical input energy into useful work at the point of use

Answer

Compressed air equipment has the highest maintenance costs of any utility

Answer

Air compressors require three-phase power which costs more

Answer

Compressed air cannot be stored, requiring constant generation