NEMA (National Electrical Manufacturers Association) and IEC (International Electrotechnical Commission) are two major standards that define motor design, with the primary difference being the geographic focus and design philosophy. In Singapore and the Asia-Pacific region, the IEC standard is overwhelmingly prevalent.
| Feature | NEMA (North America) | IEC (Global) |
| Measurement | Imperial (inches, HP) | Metric (mm, kW) |
| Frame Size | Fewer, more robust sizes. | More standardized, compact sizes. |
| Overload Capacity | Includes a Service Factor (SF), allowing temporary overload (e.g., 1.15 SF). | No Service Factor; motors are rated for specific continuous duty (S1). |
| Efficiency Classes | Defined by Premium Efficiency levels. | Tiered system: IE1, IE2, IE3, IE4, IE5. |
NEMA motors are the standard in North America; their design philosophy favors a more robust construction and fewer, larger frame sizes, which is why NEMA motors often include a Service Factor (typically 1.15). This factor means the motor can safely handle up to 15% overload for short periods, providing a safety cushion.
IEC motors are dominant globally, including in Singapore, and are designed for compactness and application-specific needs. They utilize a metric-based system for dimensions and typically do not have a built-in Service Factor, meaning they must be sized exactly for the job. IEC also uses a more granular, tiered system for efficiency, ranging from IE1 (Standard) up to IE5 (Ultra-Premium), allowing for finer selection based on energy goals; this tiered system is key as Singapore legally mandates a minimum of IE3 (Premium Efficiency) for many industrial motors. If you work globally, you must understand both standards.