We receive a few calls each quarter from our customers and their contract manufacturers mistakenly thinking our fans do not pass their incoming inspection testing.  Many do a quick check by running the fan at full speed and measuring the RPMs via the pulse tach output lead wire and get a different value by either comparing it to their “golden test fan” or from the published spec causing them concerns.

Here is a brief explanation on why they are seeing a discrepancy.

Nominal Rated Speed with a +/-15% Tolerance

As an example, let’s look at our 9WL0412P3J001 fan model.  The customer tests the fan and measures 17,000 RPM.

As you can see from the published catalog sheet found in our website or hard copy catalog, at full speed (PWM duty cycle is 100%) the rated speed is 17,500 RPM. This is the nominal speed based on testing the fan in an open test bench (free air condition) which is the industry wide practice by all DC fan suppliers for published specs.

SANYO DENKI Specification on cooling fan

However, when we compare it to the full specification for this model, the 500 RPM difference is fine and well within the rated speed spec of +/- 2,600 RPMs or +/- 15% at full speed, as we see below:

This variation in speed is attributed to the combined variations found in the windings (stator), discrete components and the manufacturing processes (lot to lot).

Note each SANYO DENKI fan is tested to ensure it meets our specs by doing 100% in-line testing and final testing.

 In closing, all DC fans from SANYO DENKI (and all other suppliers) have a speed tolerance, so when in doubt, please feel free to contact your local SANYO DENKI AMERICA sales office or sales rep and we will be glad to help. 

Written by Gary Masessa


SANYO DENKI has been a trusted provider of cooling solutions for various industries, with fans being a crucial component in many advanced devices. Contact us for a quote, or to discuss your device's customization requirements.

Our experienced application engineers and field engineers will provide support on the customization or any other technical support for your equipment. Contact our representatives or distributors to start discussing your next project.

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