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Energy Efficient Electric Motors

June 2008 | Link | John Herbert

Globally, electric motors consume 3/5th of the all the electricity generated, therefore improving the efficiency of every electrical motor should be a high priority for everyone.

But there is more to the story than just efficiency, optimizing the usage of the electrical motors to met the actual load provides more opportunities to lower you operating costs, and lower pollution that electricity generation creates.

Motor Efficiency

First, we must ask what is efficiency and then what is high efficiency? We need to ask the question since everyone has a efficient view of hi-efficiency.

5.4.1     Motor Efficiency
Except for motors which are components of package equipment, any polyphase induction motor having an output power of 5kW or greater that is expected to operate more than 1,000 hours per year should use "high-efficiency" motors tested to relevant international standards such as IEEE 112-1991 or IEC 34-2. The nominal full-load motor efficiency shall be no less than those shown in Table 5.1.

Table 5.1: Minimum Acceptable Nominal Full-Load Motor Efficiency for Single-Speed Polyphase Motors 

Motor Rated Output (P)

Minimum Rated Efficiency (%)

5kW<P<7.5kW

84.0

7.55kW<P<15kW

85.5

15kW<P<37kW

88.5

37kW<P<75kW

90.0

75kW<P<90kW

91.5

P>90kW

92.0



Globally, electric motors consume 3/5th of the all the electricity generated, therefore improving the efficiency of every electrical motor provides energy efficiency improvement opportunities.

But there is more to the story than just motor efficiency, optimizing the usage of electrical motors such that they met the actual load requirement provides other opportunities to lower your operating costs, and lower pollution that electricity generation creates.



It is worth repeating that the cost of preventing pollution (entering the environment) is very much lower than the cost for remedial work to remove polluants from the environment after contamination. This is the p2e2 principal, gain the benefits of energy efficiency, lower energy biils, and lessen the environmental impact today, before the cost of remediation hits your profits tomorrow.


Motor Efficiency

The Hong Kong Code of Practice for Energy efficiency clause 5.4.1 Motor Efficiency states:

"Except for motors which are components of package equipment, any polyphase induction motor having an output power of 5kW or greater that is expected to operate more than 1,000 hours per year should use "high-efficiency" motors tested to relevant international standards such as IEEE 112-1991 or IEC 34-2. The nominal full-load motor efficiency shall be no less than those shown in Table 5.1.

Table 5.1: Minimum Acceptable Nominal Full-Load Motor Efficiency for Single-Speed Polyphase Motors 

Motor Rated
Output (Power)
Minimum
Rated
Efficiency
(%)
5kW<P<7.5kW 84.0
7.55kW<P<15kW 85.5
15kW<P<37kW 88.5
37kW<P<75kW 90.0
75kW<P<90kW 91.5
P>90kW 92


So that is clear right? I am sure I am not alone noticing the "escape" clause for package equipment. However, at present the HKCOP for electrical installations is not complusory.

They is still plenty of confusion in the industry regarding what is and what is not an energy efficient motor, partially caused by the standards themselves.

Many buyers believe that high efficiency motors are fitted as the "standard" in all equipment, however as indicated above reliance on a standard for packaged equipment can be deceiving.

Engineers, industry, equipment manufacturers, and specifications need to avoid these abstract terms like "high efficiency" and actually state real values.

Electric Motor Applications

Electric motors are ubiquitous,an integral part of modern life, they are used everywhere, in most appliances, manufacturing processes, air conditioning units, fluid handling, and the like.

They are relatively inexpensive when compared to their operating cost. Typically, an electric motor will consume enough electricity in the first nine - twelve of months of operation, exceeding its initial capital cost. That's important because operating in-efficient motors every year after year just wastes energy. Replacing an in-efficient motors is a sound investment.

Variable Speed Drives and Controls

It is critical to match the motive power to the actual load.Even in the 21st century, we still see over sized motors wasting energy. Often motors are running at full speed during periods of part load, where as this was difficult in the past to control, modern Variable speed drives can easily lower the operating speed in real time to match the actual load.

In most applications, including fans, lower the speed lowers the power consumption significantly, and reduces operating cost due to extending operation life of the motor.

Further Information

To learn more above energy efficient electric motors and operation contact Mr John Herbert at our Hong Kong office, telephone +852 2335 9830

keywords: energy efficient motors, motor operation, high efficiency

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