CEM - Certified Energy Manager Electrical Systems and Motors Questions and Answers

Question 1

A manufacturing facility has a consistent electrical load of 500 kW.
The plant's power factor is measured at 0.75 lagging.
To avoid utility penalties and reduce demand charges, the facility manager wants to improve the power factor to 0.95 lagging.
Which of the following is the closest to the required size of a capacitor bank (in kVAR) to achieve this correction?

Accepted Answer

276 kVAR

Answer

211 kVAR

Answer

440 kVAR

Answer

661 kVAR

Question 2

An existing 100 HP motor operates at 80% load with an efficiency of 90%. It is replaced with a new 100 HP NEMA Premium motor that operates at 95% efficiency at the same load. Assuming the motor runs 6,000 hours per year and electricity costs $0.10/kWh, what are the approximate annual energy savings?

Accepted Answer

$2,785

Answer

$1,963

Answer

$2,488

Answer

$3,140

Question 3

A variable frequency drive (VFD) is installed on a centrifugal pump motor. If the VFD reduces the motor's speed to 70% of its original speed, what is the approximate reduction in the power required by the motor?

Accepted Answer

66%

Answer

30%

Answer

51%

Answer

90%

Question 4

Which of the following best describes a facility with a high electrical load factor?

Accepted Answer

The facility's energy consumption is consistent with few and low peaks in demand.

Answer

The facility has a very high peak demand compared to its average energy use.

Answer

The facility operates for very few hours per day but consumes a large amount of power.

Answer

The facility has a low power factor, requiring significant reactive power.

Question 5

An energy manager is specifying a replacement for a failed 50 HP, three-phase induction motor. To maximize long-term energy savings, which motor designation should be prioritized?

Accepted Answer

NEMA Premium Efficiency

Answer

NEMA Design D

Answer

IEC Frame

Answer

Standard Efficiency (EPAct)

Question 6

An energy audit is performed on a 4-pole induction motor with a nameplate synchronous speed of 1,800 RPM. Using a tachometer, the actual full-load operating speed is measured to be 1,755 RPM. What is the motor's slip?

Accepted Answer

2.5%

Answer

97.5%

Answer

45 RPM

Answer

1.02%