I've built my own CNC router and the last job is to get the VFD working. I installed everything and tested the VFD with the onboard speed control and everything worked okay. I admit I did not pay much attention to the installation sequence because it's pretty straight-forward. However, after I hooked up the 0-10V control and retested using the controller to control the speed, the VFD wouldn't maintain speed.

I went through various forums and spoke to the controller board manufacturer but drew a blank. The VFD vendor (G-Penny) didn't respond. When I put everything back to factory settings, the motor ran up to full speed regardless of the potentiometer setting. So, assuming the VFD was damaged, I bought a replacement.

This time I was meticulous about the installation and wrote down each step (see below) but ended up with exactly the same problem. The symptoms are as follows:

1. When setting the speed in Mach 4 (MCI: S6000M3), the motor varies between 1700 - 3300 RPM with a cycle period of ~5sec.
2. The control voltage is steady at 2.51V
3. There is 115VAC coming from the VFD earth terminal.
4. There are no error codes displayed on the VFD.

I could really use some help here to figure out what's going wrong.

Here are the installation steps and further information about the setup:

VFD CONNECTION AND TESTING SEQUENCE

************************************************** *****************************
SYSTEM
MOTOR: G-PENNY 1.5kW WATER COOLED (4 x 1.5mm2 SHIELDED CABLE)
VFD: HY01D523B, 1.5kW
INPUT VOLTAGE: 1-ph, 230 VAC, 50Hz, 20A FILTER
CONTROLLER: WARP 9 ESS, MB3 Interface Board
CAM SOFTWARE: MACH 4

************************************************** *****************************

* STAGE 1
1. Connect motor output terminals (U, V, W, E)
2. Connect mains input (L, N. E)
3. Switch on power and check input voltage (233.7VAC, 50Hz).
4. Press 'Run' and check speed control with operator potentiometer.
5. Switch off power.

Result: VFD and motor functioning correctly.

* STAGE 2
1. Turn on power to CNC controller (VFD is OFF).
2. Set spindle speed in MACH 4 (G-Code: SxxxxM3)
3. Check analog voltage output from controller according to RPM. (Measured at the VFD - before connection)
4. Check FOR/REV relays.
5. Switch off power

Result: RPM Voltage
6000 = 2.51V
12000 = 5.10V
18000 = 7.53V
24000 = 10.24V
Relays: Working

* STAGE 3
1. Connect 0-10V analog signal to VFD: ACM and VI.
2. Connect wire link on VFD from DCM to FOR.
3. Move VFD jumper from VR to VI.
4. Switch on VFD power.
5. Set PD070 to 0 (0-10V)
6. Set PD001 to 1 (external terminals)
7. Set PD002 to 1 (external terminals)
8. Turn on power to CNC controller.
9. Set spindle speed to 6000 RPM (G-Code: S6000M3).
10 Check control voltage.

Result: FAIL. Spindle motor speeds up and slows down between 1700 - 3300 RPM.
Analog control voltage steady at 2.51V.
No error codes displayed.

* TESTS
MOTOR & CABLE CONTINUITY (DISCONNECTED)
U - V = 2.4R
U - W = 2.4R
W - V = 2.4R
E - U = O/C
E - V = O/C
E - W = O/C

VFD
When the VFD is returned to factory configuration, the control pot no longer works; motor accelerates to full speed.
115 VAC coming from motor earth connection (even with motor & earth disconnected).