What BecSpec cannot tell you.

Shaft dimensions are not available

Shaft diameter, shaft length and keyway details are not in the GEMS register, and BecSpec does not source them elsewhere — see data and sources for why. These are frequently the deciding factor in whether a replacement motor works, because they determine whether your existing coupling, pulley, sprocket or gearbox will mount.

Two motors sharing a frame designation do not necessarily share a shaft. Always check the manufacturer's dimensional drawing before ordering.

Full-load speed is not available

The register records pole count but not the actual speed under load. BecSpec calculates and clearly labels the synchronous speed — 1500 rpm for a 4-pole motor at 50 Hz — but a real motor runs slower than this because of slip, typically by one to five percent depending on design and loading.

If your application depends on a specific driven speed, or you are matching an existing motor's output speed, take the figure from the nameplate rather than from BecSpec.

Most registrations describe families, not models

This is the limitation most likely to mislead. A single GEMS registration often covers a whole product family, and the mounting, voltage and enclosure fields then list every option available across that family rather than the configuration of the model number shown.

In the current data, 84% of records list more than one mounting arrangement. When BecSpec marks a match family-level, it means a compliant variant with that specification exists in the family — not that the specific model number shown is supplied that way. Use the "Model-specific values only" filter if you want to see only records where the register describes a single configuration.

Registration is not a compatibility statement

GEMS registration exists to record minimum energy performance compliance. It is not a fitment database and was never intended as one. BecSpec uses it because it is comprehensive and openly licensed, not because it is complete for selection purposes.

Things no dataset can answer

Even with perfect product data, these remain yours to determine:

• Whether the driven load's torque and inertia suit the motor's starting characteristics.
• Duty cycle, starts per hour, and thermal implications of your application.
• Ambient temperature, altitude, and derating that follows from them.
• Whether the motor will be run on a variable speed drive, and whether it is rated for it.
• Hazardous area requirements, which are outside this dataset entirely.
• Available space, cable entry orientation, terminal box position, and foundation.
• Electrical protection, cable sizing and switchgear coordination.

Data quality caveats

The register is supplier-submitted, and the submissions vary in quality. BecSpec normalises what it can and refuses to guess at the rest. Specifically, in the current snapshot:

• 67 records carry a frame designation BecSpec could not read as either IEC or NEMA — vendor-specific codes and free text. These are shown exactly as supplied, uninterpreted, and are excluded from frame matching.
• 46 records use NEMA frames rather than IEC. They are never matched against IEC frame requests.
• A handful of records carry voltage or mounting entries BecSpec could not parse. Those fields are reported as not stated rather than being filled with an assumption.
• Where a supplier entered nothing, BecSpec shows "not stated" — it does not substitute a typical value.

This is an experiment

BecSpec V1 covers one product category and is being run to find out whether a technical matching tool is genuinely useful to people trying to specify or replace equipment. Supplier connections are not live yet. If something here is wrong, missing or misleading, that is worth knowing about.