Matthew Conville, MBA, PE
EASA Technical Support Specialist

Before putting an AC machine into service, make sure its duty rating matches the application requirements. Otherwise, there’s a good chance excessive heat will degrade the machine’s windings.

Applications are not all created equal. For example, a crane motor doesn’t require the same duty rating as a punch press motor of equal horsepower that runs continuously. Likewise, a chop saw motor wouldn’t need the same duty rating as a pump motor that operates 24-7-365. If the motor must operate at variable speeds other than its nameplate base speed, its turndown ratio is another consideration.

NEMA Std. MG-1-1.40 and IEC Std. 60034-1, Clause 4 describe the duty classifications for the respective standards.

• NEMA duty classifications
• IEC duty types with "S" ratings
• Turndown ratios
• Questions to consider

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When an electric motor will be stored a long time before being placed in service, you must take certain steps to ensure it will be suitable for operation when it’s needed. One practical limitation to recognize is that much of what is done when preparing a motor for long-term storage must be undone when it is moved into operation. Storage procedures generally depend on the size of the motor and whether it will be out of service short term (several weeks) or long term (several months).

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By Gene Vogel
EASA Pump & Vibration Specialist

An important step when selecting a centrifugal pump and an electric motor for an application or when troubleshooting operation issues is to determine how much power the pump should be using. The “by-the-book” approach references the pump curve, which shows the power requirement for the pump’s range of operation (head and flow rate). While that’s the best approach, a simple, universal formula based on the relationship of power, head, flow rate, and efficiency can provide realistic estimates for general planning or primary troubleshooting.

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By Jim Bryan
EASA Technical Support Specialist (retired)

The Institute of Electrical and Electronics Engineers (IEEE) has published a new standard: IEEE Std. 3004.8-2016, “Recommended Practice for Motor Protection in Industrial and Commercial Power Systems.” If you’re an electrical professional who deals with a broad spectrum of motor protection schemes, including low- and medium-voltage AC and DC motors, then you need to become familiar with this standard.

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By Gene Vogel
EASA Pump & Vibration Specialist

If you work with electric motors and pumps, you’ll eventually encounter a pump curve and one of its key parameters — best efficiency point (BEP). The BEP is the point on the curve where the pump operates most efficiently. Unique to each pump, the BEP is a product of both impeller design and several related pump curve parameters.

This article covers:

• Pump efficiency
• Effect of flow rate
• Effect of impeller design on BEP

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