Wiring A Vfd To A Momentary Pushbutton Switch (update)

A while back I had a request for a design to use momentary switches on a VFD (TECO JNEV) that did not support 3 wire control. Attached is a schematic using momentary switches and latching relays that could be used on different machines that includes forward/reverse and stop. The left side of the relay is the VFD input controls, the right side of the relay is the latch. They are interlocked so you always need to go through stop to change directions. This was used on a lathe VFD conversion, also very simple and inexpensive. Not sure of the need for a relay coil diode for smaller relays and when using a separate power supply.
VFD Latching Relay Wiring Diagram.jpg Latching Relay with Momentary Switches and Proximity Limit Switch.jpg
 
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derf said:
What is the advantage of a momentary switch?
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Cant be accidentaly left in the on possition after a power outage, appart from that i guess its just preferance.

All european stuff seems to have buttons appart from bench grinders which seem to have switches.

I do find it easy to hit the button if i need to stop.

I had factory installed buttons on my old 9x20 (cm) lathe but they were on the top, bad place to put them i reckon as you could lean on them accidentaly or drop somthing onto them, opps :) .

Stuart
 
Okay So I redesigned the latching relay circuit to include an automatic reversing feature. It keeps the spindle rotation correct in accordance with the Forward & Reverse buttons when switched into either High or Low gear range. I had to add another relay so I just built a new board, I also added a terminal block. The status is sensed by a microswitch contacting the Hi/Lo shift lever. I know some eyes are rolling However. I will be converting the mill to CNC and this will let the computer will know the speed range its in. In the meantime, it will prevent bonehead mistakes, which I am perfectly capable of.
IMG_8672.jpg IMG_8673.jpg IMG_8681.jpgIMG_8677.jpgIMG_8683.jpgIMG_8675.jpg
I also added a second VFD to power the Z Axis motor, and upgraded and relocated the Up/Down switch to the head, where it's more convenient.
One thing I discovered, if the Hi/Lo switch is actuated while the spindle is running the VFD stops then reverses. I can add a button in parallel, this will make a great tapping feature like the instant reverse button on the downed handle of a SIEG X3. Guess I'm not done yet...
 
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Eddyde said:
Thanks gr8legs, for the suggestion.
However I don't think it will work on this model, I went through the entire manual,several times, searching for a way to change the switch parameters to momentary, because I thought "there must be a way". The only thing I found was a way to change the switch status from NO to NC... It only gives three choices; "Run Forward-Stop, Run Reverse-Stop" 2 switches. (this is the one I used)
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The manual that came with my L510 is not complete. It is missing chapters 6-11. Some of those chapters have some good stuff in them. Chapter 7 describes external control modes. You can load it online at:

https://www.tecowestinghouse.com/Manuals/L510_instruction_manual.pdf

Look on page 7-3. There is a diagram showing use of two momentary pushbuttons (one to start, one to stop). Requires changing parameter 00-04=2. "Three wire control mode".

So far I am not a happy camper (just got the VFD). It gives my 2 HP a horrible resonance starting at 28 and continuing to 56 Hz. Like shake my workbench vibration. I have a 1 HP JNEV, and when I hook that up, the motor is smooth as silk. Hopefully I can tune this thing a bit better, ow it is going back!
 
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Yeah thats pretty much the manual I have, I know the switch configurations they offer but they didn't exactly fit what I wanted to do, hence my circuit. Hmm.. not sure why your getting the weird resonance, I have a 2 hp and it works fine, maybe it's a defect in that drive?
 
Eddyde said:
Yeah thats pretty much the manual I have, I know the switch configurations they offer but they didn't exactly fit what I wanted to do, hence my circuit. Hmm.. not sure why your getting the weird resonance, I have a 2 hp and it works fine, maybe it's a defect in that drive?
Click to expand...

I was glad I had a Teco JNEV on my shelf to test the motor out, otherwise I would have been yelling at the company I bought it from... came in a cardboard box split down the side, with the motor loose from the wood base it was bolted to and a shaft punched through the side of the cardboard. I thought "ohh no", and quickly hooked it up, and the dang thing just about fell off my workbench it was shaking so bad.

I will have to check if I have some 100X probes so I can hook my o-scope up and check the output. All three phases are running the same voltage, but that really doesn't mean much.
 
A scope would certainly find if a phase had an irregular waveform or other anomaly. Please keep me abreast of what you find.
 
Well this sucks.

My JNEV gives me a nice shaped signal output on my o-scope, looks exactly like what I would expect. My L510 gives me a real garbage looking signal, not surprised it is trying to shake the motor to pieces.

Looks like I am going to have to RMA the L510. I will take a closer look tomorrow just to make sure that I am not missing something.
 
Some VFDs support 3 wire control, some do not. It seems an odd thing to omit but many do. This is definitely something to pay attention to when buying a VFD, as very often one will want to use the existing push button station.
 
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