VFDSPINDLE VFD & CNC spindle wiring, sizing and setup

Spindle connector pinouts: how to find yours

There is no universal pinout for the aviation connector on a CNC spindle. Sellers list the same connector with different wiring, and the same seller changes it between batches. This page will not give you a pin table — it gives you the ten-minute procedure that works every time.

Why we do not publish a pin table. A wrong pin table is worse than no pin table: it gets screenshotted, reposted, and a year later someone earths a phase because a four-pin plug looked the same. The measurement below takes longer to read than to do.

What you are looking for

Open the connector and count the cores. Then work through this:

Identification by measurement — not by colour
MeasurementReading you wantWhat it is
Between pairs of coresThree cores with equal, low resistance between every pairThe three windings: U, V, W
Core to connector shell / spindle bodyOne core at ~0 Ω to the metal bodyProtective earth
Remaining cores, to each otherA pair with a definite resistance, open to the bodyTemperature sensor (see below)
Every winding core to the bodyOpen — ideally megohmsConfirms the windings are not earthed

The procedure

  1. Disconnect the spindle from everything. Not just switched off — unplugged.
  2. Set the meter to resistance and zero-check the leads by shorting them. A 0.3 Ω lead resistance matters when the winding itself is 0.5 Ω.
  3. Find the earth first. Probe each core against the bare metal of the connector shell or the spindle body. Exactly one should read near zero. That is your PE, and it goes to the earth terminal on the drive and to the frame. If nothing reads to the body, the spindle has a separate earth lug — find it; it must be bonded.
  4. Find the three windings. Measure every pair among the remaining cores. Three of them will form a triangle of equal low readings. Those are U, V and W. Their order does not matter yet — it only sets direction, and you can swap two later (see wiring basics).
  5. Whatever is left is the sensor, if anything is. Two cores with a resistance that is neither zero nor open, and no connection to the body, are a temperature sensor. Measure it at room temperature and write the value down — you will need it later if you wire it to a monitor.
  6. Confirm no winding is earthed. Each of the three against the body should be open. If one reads anything other than open, stop and do not power up.

Common core counts and what they usually turn out to be

Written as “usually” deliberately. Treat it as a starting hypothesis, not an answer.

Core count → likely allocation. Verify every row with a meter.
CoresCommonlyWatch for
3U, V, W — earth via the body or a separate lugAn unbonded body is not an earth path
4U, V, W, PEThe most common arrangement on air- and water-cooled router spindles
5U, V, W, PE + one sensor return sharing the earth, or a shieldSensor may be referenced to PE rather than having its own return
6–7Adds a sensor pair, and on ATC spindles, solenoid or position feedbackDo not assume the extra cores are spare
Colour codes are not reliable either. Many spindles ship with numbered cores (1, 2, 3, 4) rather than coloured insulation, and where colours exist, green/yellow as an earth is not universal. Measure for the earth — do not assume it.

About the temperature sensor

Spindle temperature sensors come in several families and they are not interchangeable: a resistance that rises with temperature (PTC / PT100 / KTY-type), or a switch that opens at a threshold. They behave completely differently at the monitoring end, and connecting the wrong monitoring to the wrong type gives a spindle that either never alarms or alarms continuously.

Two honest options:

We will not guess which yours is from a photograph of a connector.

Once you know the pinout

Label the cores before you close the connector, and write the pin numbers on the spindle with a marker or a label. The next time — when you move the machine, replace the cable, or help someone else on a forum — you will not have to do this again.

Then go to the wiring diagram and land them.

Parts

Connectors and cable

Questions

Why is there no pinout table on this page?

Because pinouts vary between makers and between revisions of the same model, and a wrong one gets screenshotted and reused for years. A meter and a procedure do not go stale.

How do I find which pin is earth?

With the spindle disconnected from everything, measure resistance from each pin to the spindle housing. The earth pin is the one at or very near zero ohms.

Can I identify the phase pins with a meter?

Yes. The three phase pins show a low and roughly equal resistance between each pair, and a much higher resistance or an open circuit to the temperature sensor pins.

Sources and method

Three kinds of statement appear on this page, and each is labelled where it occurs:

Standards and documents

Further reading