PM-1236 motor issue

[jbolt]

I set my lathe up with 2-stage braking but kept the manual brake. I prefer to have the manual brake for safety. The manual brake will stop a large chuck from full rpm faster than the VFD. If the VFD faults it freewheels. The foot brake is also quicker than hand lever.

 

[tino_ale]

So.... may sound like a joke, but I'm just completing my VFD conversion now. That's what a newborn will do to your hobbies apparently

Anyhow, I've done the bulk of the conversion and I have it working 75%

I have a defective jog direction button that I need to replace
I have not re-wired the status light yet, I just need to buy a LED light to limit current draw from the 24vdc VFD supply
I am not entirely sure if the "no resume on startup after power loss" works, I need to double check that one
I have not programmed the two speed dynamic braking but I know what to do (thanks to you), and it's only one wire more than my current setup

I dit not have shielded wires on hands, so I went ahead without, that may be the next upgrade down the road...

I have all these things covered and I can't thank you enough for the inputs. Using the schematics has been invaluable. Now that I've wrapped my head around the global logic of the interlocks, I think it is a KISS implementation, nicely done and elegant.

I am just a little confused about the initial settings that need to be done at the VFD for it to run the motor perfectly.
I have the Hitachi WJ200 VFD drive

I have noted down these parameters to run the motor in the 40-80Hz window :
- A003 Base Frequency : 60 Hz
- A004 Maximum Frequency : 80 Hz
- A011 Start Frequency : 40 Hz
- A012 End Frequency : 80 Hz (redundant with A004 ?)
- A082 Automatic Voltage Regulation : 230 VAC
- B012 Motor Current Rating : 5.4 Amps
- H004 Motor Poles Setting : Four Poles

Am I missing anything that should be initialized ?
Also should I / how do I use the "auto-tune" feature ? Is it actually needed to run the motor at it's peak performance ?

Thanks for any input
BTW, the smoothness of the setup is just beyond my expectations. If I had known I would have ordered the lathe with the VFD setup from day 1.

 

[mksj]

The parameters should be pretty much the same as the Basic VFD COnversion (see below). Top speed on the motor probably 80 hz. The WJ200 just has the motor kW, no amps, 4 pole is the default. Make sure the correct motor voltage is set, I believe it is 220V. Run the autotune after everything is setup and working.

 

[tino_ale]

Thanks !

I have already set the core parameters (not all that are listed in gree in this document, some of them seem pretty advanced and optinnal), but it already works 100% nonetheless.
I have tested all the interlocks and safety mechanisms, they all work as they should. I have tried combining scenarios, there is no problem whatsoever.
Great stuff !

I have all that I wanted, including the dual speed dynamic brake (harder for emergency, more conservative for normal operation). I need to add an external resistor though as anything shorter than 2 sec. will trip the VFD in dynamic braking.

Looks like I only need to run the auto-tune now. I'm also curious about the A044 V/f characteristic curve 03Sensorless vector parameter, will search about that.

Man that VFD setup really is much nicer that the rest of the lathe is !

 

[mksj]

Sensorless vector give much better motor control, in particular at lower motor speeds. It uses the motor windings/currents to feedback position of the motor stator to the VFD so it can make continuous corrections which give tighter motor control. The default is what as known as V/Hz control which does not use feedback. Nice that you have it up and running, I recall your situation a number of years ago with a failed single phase motor. You do want to add an external braking resistor, they can be picked up inexpensively on eBay or electronics house, anything in the 50-75 ohms, 300-500W.

 

[tino_ale]

Hi,

I got a 50ohm 500W resistor. But there is a problem...

I connected the resistor to terminals 1 and 3 on the upper connector line. Those are referred to RB and + terminals. I mistaken the first time and connected the load to RB and - terminals (positions 1 and 4) before I corrected my mistake.

Anyway either way the second I plug the machine my 30mA differential trips.

I isolated the resistor and measured 128 volts at the resistor body (ground as reference).

For the sake of the test I set b090 to 10% duty cycle and surprisingly the dynamic brake works ?!

I have tried connecting only one terminal at the time from the VFD to the resistor. Either RB or + terminal connected to the resistor alone produce the same effect which is instant trip of the differential. I figure some current can leak from either terminal to the ground through the resistor casing.

I have opened the VFD to check of my first mistake did any visible damage but there is no damage to be seen.

With no resistor connected I read those AC voltages at the VFD terminals (ground as reference) :
RB : 34V
+1 : 129V
+ (connected to terminal +1 with a jumper) : 129V
- : 130V
Neutral is approx 1V floating
L1 is at 226V

The 3 motor terminals (while not running) are at 109V.

Do these readings look normal ?

Do I just have a poorly isolated resistor that needs replacing or do I have a bigger issue ?

I tried to measure the isolation of the resistor but I don’t have proper equipment. At 35 volts DC between either terminals and the resistor casing, I barely read 1mA at my multimeter. That is not much but I supposer more than it should!

Thanks

 

[mksj]

If you are looking at leakage with a GFI (neutral wire), they do not work well with VFD's, if one is required then you need an expensive industrial type specifically for use with VFD's. Using a braking resistor should not change things, there should be no measurable resistance between the resistor casing and the leads unless it is defective. You should be ably to measure it with an ohm meter the resistance of either end of the resistor to the case and it should be in the megaohm range. It is DC on the buss not AC, the excess voltage is shunted through the resistor only with fast stopping. It is possible you damaged the resistor when it was connected to RB and - terminal as I believe this would be similar to placing the resistor between the high voltage DC buss and 0V. When measuring AC you probably need a LowZ voltmeter to eliminate phantom voltages that can be induced in the AC wiring. The braking terminals modulate the voltage/current through the braking resister. The braking duty cycle is the % varies on a number of different parameters.

 

[tino_ale]

Hi,
I got a replacement 50 ohm resistor and everything is now working as it sould. The first one was either defective or damaged by me. No more differential trips, dynamic braking rocks !

I have set 3 seconds of braking time for normal operation and 1.5 seconds for emergency stop. I feel those are adequate.

As for acceleration time I have set 4 seconds. 3 seconds trips the overload protection at highest gear and highest Hz setting, I am using linear acceleration/deceleration. I’m sure some tuning would allow 3 sec acceleration though. It’s good enough though.

Thanks again ! I am relieved that I have not smoked something in my VFD.