A buyer searching for VFD is usually trying to stop a bad substitute. An electronic part is specified by the electrical job, the package the assembler can solder, and the temperature inside the enclosure. The notes below are selection criteria for a VFD. They are not a catalog promise. Confirm every rating on the current datasheet, drawing, or test report for the revision you will receive.
What has to be true of VFD
An electronic part is specified by the electrical job, the package the assembler can solder, and the temperature inside the enclosure. For a VFD, start from the duty, then the interface to the rest of the machine or the room, then the document that proves the claim. A lower price that leaves one of those blank is a different product.
VFD is easy to confuse with Solid State Relay. If the quote could be read as either, add the line that separates them: the rating, the fitment, or the standard named below. Link the drawing number to that line so receiving inspection can reject the wrong one.
Numbers that change the quote
| Line | What to write for VFD |
|---|---|
| Voltage and current | Continuous ratings at the real ambient, plus the peak and how long it lasts. |
| Interface | Pinout, protocol, and whether levels are 3.3 V, 5 V, or a field signal such as 4–20 mA. |
| Package and mount | Footprint, pitch, and whether the assembler can rework it. |
| Temperature | Commercial versus industrial range, measured in the enclosure you will actually build. |
| Supply life | A second source or a stated longevity, not only today’s distributor stock. |
| Compliance file | RoHS declaration and any safety report, tied to the exact part number. |
How to compare two offers
Lay both quotes for VFD on one sheet and line up voltage and current, interface, and package and mount. If a cell is empty, the offer is not finished. Ask for the missing line in writing. When those match, the honest difference is lead time, the test evidence, and who carries the warranty. Do not average a fully specified VFD with a cheaper line that omitted voltage and current.
Documents worth having before the deposit
Ask for the datasheet revision, a recommended footprint, and the moisture-sensitivity level if the part is surface-mount. The file should name VFD and the revision, not only the supplier’s homepage. A factory quality certificate such as ISO 9001 can sit beside that file. It does not replace it.
Failures that show up after delivery
- Leaving the second source unnamed until the first source goes on allocation.
- Buying the development-board part number instead of the production silicon.
- Treating a logic-level input as if every power device fully enhances at 3.3 V.
On a VFD, the expensive version of the first mistake is discovering it after the goods are in the crate. Put the rejection condition in the purchase order while the supplier can still restate the offer.
A worked RFQ line
Use this shape, then replace the brackets with your duty: “VFD — State voltage, continuous current, package, industrial temperature, and the datasheet revision.” That sentence is a template, not a rating of any brand. If a supplier’s datasheet uses different units, convert them onto this sheet so the next offer can be compared.
Where words like waterproof / IP65 belong
Searches often add a constraint to VFD: waterproof / IP65, or IP67. Keep those on this page. IP65 in IEC 60529 means dust-tight and protected against water jets. Write that code if hoses are the real exposure. The word waterproof alone does not name a test. IP67 is dust-tight plus a defined temporary immersion. It is not a rating for living underwater, and it says nothing about sunlight or salt. If you need a third constraint, add it as another line on the same drawing. A second URL that only swaps the adjective does not give a buyer a second fact.
Related in this section: how to specify Solid State Relay.
Questions buyers actually ask
What should an RFQ for VFD include?
State voltage, continuous current, package, industrial temperature, and the datasheet revision.
Is a cheaper VFD the same part?
Only if voltage and current, interface, and the documents match. A missing line is a different offer.
Do waterproof, OEM, or IP words need their own page?
No. For VFD they are extra lines on this specification. Ask for the test or the drawing that gives the word a value.