Adding a VFD to my Enco 13x40 lathe

I decided to take the plunge and add a VFD to my Enco 13x40 lathe.  The main reason I chose to do so was because there is chatter when I cut threads, which has been attributed to the use of a 2-pole single-phase AC motor on the lath.

So I have switched to a 4-pole, 3-phase AC motor.  I hope it will work out OK.  The maximum speed is higher, so I'm a bit concerned about that.  But I can reduce the speed with my VFD, and I can choose an appropriate gear range.  So I think it will be fine.

I had to make a spindle adapter to adapt my new motor to the old pulley.  I may choose to detail that more in the future, but I didn't take any pictures while it was apart, so I'll not tell that part of the story for now.

My plan is to have everything work through the standard lathe controls, rather than running everything through the VFD panel controls.  I intend to use a potentiometer to control the speed, rather than using the up and down arrows on the VFD panel, because it’s easier.

I purchased a HY01D523B single-phase, 220V, 1.5 kW (2 hp) VFD on Ebay.  For about $60, this VFD should run my lathe well.

VFD Mismatch

My VFD is listed as an HY01D523B.  But when I downloaded the manual from the internet, I found that my VFD doesn't match the manual downloaded from the internet.

The online manual for the HY01D523B, which is found in several places, including https://www.exoror.com/datasheet/VFD.pdf, describes a system parameters from PD000 to PD182.  The panel buttons in the manual don't match the panel buttons on my VFD.

My VFD has parameters from Pn01 to Pn35.  It has Run, Stop/Reset, Set, Rev/Fwd, Up, Down, Left, and Right buttons.  Hunting on the internet, I found a VFD that matched my panel, with the exception that mine doesn't have a built-in potentiometer (Askpower A131 Series).  The manual is found at hackaday.  I also had the Ebay seller send me a manual.  You can get the manual they sent me here.  This manual refers to my VFD as an A2 series VFD.

Because the function of the two VFDs is different, different wiring diagrams and programming are required.  Because I designed it for the HY-style first, I have the full design.  But since I don't have an HY-style VFD, I haven't actually tested the HY-style information.  But I believe it's right.

Factory Lathe Wiring

Figure 1: Wiring Diagram from my lathe owners manual

Figure 1 shows my lathe's wiring diagram.  As it currently exists, KM1 supplies power to the the control system with its auxiliary contacts and its main contactors make the AC available to the reversing contactors.  The main contactors of KM2 connects the motor power to the motor to make it run in forward, and the main contactors of KM3 connect the motor power to the motor to make it run in forward.  One of the auxiliary contacts on KM2 us used to prevent KM3 energizing while KM2 is energized, and one of the auxiliary contacts on KM3 is used to prevent KM2 energizing while KM3 is energized.

Figure 2 shows the overall wiring diagram for the lathe.  The box at the left shows the front panel switches, with terminal numbers.  The terminal numbers are shown on the terminal block labeled XT.  Terminal block XT is inside the power distibution box at the rear of the lathe.

Figure 2. Lathe overall wiring diagram, showing front panel switches at left and forward/reverse switch at right.

Figure 3. Lathe distribution panel showing locations of components referred to in wiring diagram.

Figure 3 shows the pysical layout of the components in the distribution box.  Note that the contactors KM3, KM2, and KM1 have numbered terminals.  We refer to the numbered terminals in the wiring diagram.

When using the VFD, we can't use any of these main contactors to switch the input to the motor; the VFD requires no contactors on its output.  However, we can use KM1 to switch the input power supply to the VFD, and we can use the auxiliary contactors of KM2 and KM3 to switch the control signals of the VFD to energize the motor in the appropriate direction.

Power Supply to the VFD

Do the following to prepare the power supply for the VFD.

1. Remove the motor cable from the relay box.  This is done by unscrewing the connections to Z1, U1, V2, and ground.  The nut is then removed from the strain relief in the box, and the cable and strain relief are taken out together.  The strain relief screw is then backed out most of the way, and the cable can be removed from the strain relief.
2. Remove the short wires that connect KM3 to FR.  They will be labeled R2 and S2.
3. Connect a wire from the S1 terminal on the top of KM3 to the left hand contact of  FR.
4. Connect a wire from the R1 terminal on the top of KM3 to the right hand contact of FR.
5. Insert a three-conductor cable rated for the current of the motor into the strain relief you removed from the relay box (I used 12/3 SJOOW cable from Home Depot).  Also insert a shielded 4-conductor cable into the same strain relief.  Tighten the strain relief screw, insert the strain relief into the box, and tighten the nut on the strain relief.
6. Connect the 3-conductor cable to ground, U1, and V2.  This cable will be the power supply cable to the VFD.

Thermal Overload

The current design uses a thermal overload relay (FR in the schematic diagram) to interrupt the power to KM1 if there is a long-term overload on the motor.  In theory, we could continue to do that as long as KM1 is on the input to the VFD, rather than the output to the VFD.  In practice, I'd rather have the thermal overload not trip out the power to the VFD, but instead trip out the run signal to the VFD.

It might be preferable to have FR connected on the output of the VFD, because that is the actual motor load.  But because FR is already wired into the box, it's easier and probably almost as good to have FR wired into the input of the VFD.

FR is currently wired between S2 and U1 and R2 and V2.  I need to adjust it to be wired between S1 and U1 and R1 and V2.  This is done by removing the wires going to the physical top of FR from the bottom of KM3, and adding new wires from the same terminals on the top of FR to corresponding terminals on the top of KM3.  The input power to the VFD now comes from terminals U1 and V1 on the lathe control box.

To prevent the thermal overload from opening KM1, I removed the two wires from the right hand side of FR and shorted them together with a machine screw and nut.  I then covered the splice with heat-shrink tubing to prevent shorts.  The wiring of the output relay of FR is described in the motor control.

Motor Control

To implement the motor control, I will do the following:

1. Add a new 6-terminal connection block to the control box.  I used two-faced foam tape to attach it. 
2. Run a wire from connector 6 of the new circuit block to the output relay of FR.
3. Run a wire from the other output relay of FR to terminal 13 for KM3, a wire from terminal 13 of KM3 to terminal 43 of KM3, and from terminal 43 of  KM3 to terminal 43 of KM2.
4. Run a wire from terminal 14 for KM2 to terminal 14 for KM3 , then from terminal 14 of KM3 to circuit 5 of the new circuit block.
5. Run a wire from terminal 44 of KM3 to circuit 4 of the new circuit block.
6. Find the cable that comes from the switch panel to the control box.  Find the two wires that come from SB3 that go to terminals 5 and 7 on the connector block at the bottom of the control box.  On my lathe, both wires were blue.  Remove these wires from terminal 5 and 7 and connect them to circuits 1 and 2 on the new circuit block. 
7. Run a wire from terminal 43 of KM2 to circuit 1 of the new circuit block.
8. Connect the four-conductor cable (see step 5 of the VFD power section) to the new circuit block.  I chose to use black for DCM(HY-style)/GND(ASK-style) (circuit 6),  red for FOR (circuit 5), green for REV (circuit 4). and white for JOG (circuit 2).

Testing Control Wiring

NOTE: DO NOT DO THIS TEST WITH THE VFD CONNECTED.  You will damage your ohmmeter because the control signals will have power.

The control wiring can be tested without connecting either the motor or the VFD.  Apply power to the lathe.  Note that there is no AC voltage at terminals U1 and V2 (now R and T).  Make sure the E-stop is released, and press the power button.   You will now see AC voltage at terminals U1 and V2.

HY-style VFD

Move the start lever on the saddle to the forward position, and you should have very low resistance between DCM and FOR.  Move the start lever to the reverse position, and you should have very low resistance between DCM and FOR and DCM and REV.  Put the start lever to the off position and press the Jog button.  You should have very low resistance between DCM and JOG.

A2-style VFD

Move the start lever on the saddle to the forward position, and you should have very low resistance between GND and FOR.  Move the start lever to the reverse position, and you should have very low resistance between GND and REV.  Put the start lever to the off position and press the Jog button.  You should have very low resistance between GND and FOR.

Control Connection to HY-style VFD

The revised schematic is shown below.  Red indicates new connections.  Note that the schematic previously had the wrong contact numbers on the additions to KM2 and KM3.  Please make sure you use Rev 2.0 if you wish to copy my work.

Figure 4. Revised wiring diagram for lathe, Rev. 2.0. Note places where connections have been cut.  Red indicates new connections.

1. Motor control is achieved by using the terminals DCM, FOR, REV, and RST.  The motor will stop whenever RST is NOT connected to DCM.  The motor will start in forward when FOR connects momentarily to DCM, and will start in reverse when REV connects momentarily to DCM.
2. Connect the DCM, FOR, REV, and RST to the DCM, FOR, REV, and SPH, respectively.
3. Do the programming to set up the FOR, REV, and JOG terminals properly.  PD001 = 1, PD044 = 01, PD045 = 05, PD047  = 07.

Control Connection to A2-style VFD

There is yet another schematic for use with the A2 series VFD Drive as shown below.  Use Rev ASK3.0 if you have the A2 VFD.

Figure 5. Revised wiring diagram for lathe, Rev ASK3.0..  This diagram should be used with the AskPower style VFD.

1. Motor control is achieved by using the terminals GND, FOR, and REV.   The motor will run in forward when FOR is connected to GND, and will run in reverse when REV is connected to GND.
2. Connect the GND, FOR,  and REV terminals in the relay box to the GND, FOR, and REV terminals, respectively, on the VFD.
3. Do the programming to set up the FOR and REV terminals properly.  Pn04 = 2.

AC Power and Motor Connections to VFD

Connect the ground, U1/R, and V2/T wires from the relay box to ground (E), R, and T of the VFD.  

Connect U,V,W, and E on the VFD to L1, L2, L3, and ground on the motor.

Test your motor to verify that forward and reverse run in the correct direction.  If they are backwards, switch any two of the U, V, and W connections and recheck.

Speed Control

Speed control is governed by a potentiometer.  The potentiometer is a 10K potentiometer, and connects between two terminals of the VFD with the wiper connected to a third terminal.

HY-style VFD

1. Connect the pot between VR and ACM
2. Connect the wiper to VI
3. Program the VFD to get the running frequency from the external input: PD002=1

A2-style VFD

1. Connect the pot between 5V_OUT and GND
2. Connect the wiper to 5V_IN
3. Program the VFD to get the running frequency from the external input: Pn03=3