Problem- New VF-2SS setup aborted

[bbrown01]

The HFO tech had to abort the setup of my new machine because the DC voltage was too high (383vdc). All the 3-phase input voltages are within Hass specifications. The transformer taps are set correctly. I'm using a properly sized rotary phase converter. Even though the input voltages are a little high they still fall into 195v-260v range. They are as follows:

L1-L2 = 248v
L1-T3 = 242v
L2-T3 = 253v

The strange thing is these voltages were measured with a Fluke 73 Series III and a Fluke 322 DVM with the same results. The HFO tech had a Fluke true RMS DVM and his measured:

L1-L2 = 245v
L1-T3 = 234v
L2-T3 = 261v

The DC voltage measured the same on all 3 DVMs.

I'm not sure what to do at this point. The HFO, factory and the phase converter manufacturer are of little help. I could buy a buck/boost transformer and reduce the incoming voltage in hopes this would solve the problem. Or I could replace the RPC with a Phase Perfect DCP-30 unit as they are known to work with the SS.

Any help would be greatly appreciated.

Thanks,
Brian

[DRD]

What is tha max spec for the DC buss voltage? If the factory can't answer your question, I would call back, its a hit and miss with hass support, some of the guys who pick the phone really know there stuff, and some don't.
My DC buss on my 08 vf3 rides around 360 to 350 volts most of the time.
Also, you may want consult with your power company.

[bbrown01]

Thanks DRD.

The DC buss is supposed to be between 310-360v.

I had PG&E out and they said they are in spec. 240v ± 5%.

All I'm getting now is finger pointing. Haas says it's the RPC. RPC vendor says it's PG&E. PG&E says they're in spec.

[Donkey Hotey]

Without an oscilloscope, you really can't establish the voltages. The phase is wrong until there is a load on the RPC. Even then, it's not perfect unless the machine is really loaded down.

Here's what you need to know about the power in that machine:

• Incoming voltage goes through the transformer and to those taps you see in the bottom of the cabinet.
• From there, the proper set of taps is chosen during setup.
• The wires go from those taps to the Vector Drive.
• Inside the Vector Drive, the wires go to a large, full bridge rectifier.
• The rectifier connects to a bank of stabilizing capacitors.

And that's the "325V" DC bus that the machine runs on.

You'll notice that nowhere did I mention 'voltage regulation' or any kind of transistors. There is no regulation. There is no control. The output voltage is simply rectified DC, chosen from the taps on the transformer. That's why it runs in a permissible range, not an absolute voltage--it's not regulated.

If the tech didn't like the DC bus voltage, then my guess is that he should have gone to the next lower set of taps. Haas should have told him this on the phone.

Also: you can't really measure the AC voltage reliably until the RPC is under load. At idle, with no load, you'll have voltage at 0 and 180 degrees with a screwed up leg 30 degrees from one of those. This is getting a bit technical but this is what the no-load, perfect 120V legs of incoming voltage would look like on an oscilloscope:


The Black line is what the perfect incoming power would look like without capacitors (on a proper three-phase power supply). The capacitors are there to smooth it even further.

The Red line is the same leg voltages with an unloaded RPC. The input voltage in the chart above is identical in both cases. The only thing that changed is the unloaded phase angle in the RPC. That phase angle shifts closer to the proper--0,120,240 positions as you load up the RPC. In plain English: the red line will morph into the black line as the load increases on the Haas.

That's probably more than you wanted to know but the point is this: his meter may be measuring those short-lived, wild peaks, when the RMS voltage is right in the ballpark.

Regardless of what his meter read, if the DC bus voltage is high, move it to the next lower set of taps and start over. My hunch is that once the servos are running and the RPC gets a load, that 368V bus voltage (at rest) will drop down into the 350V range. If that's still too high, drop it down to the next set of taps and remeasure.

[bbrown01]

Donkey,

Thank you for taking the time for this detailed response. I have a couple of follow-up questions if you don't mind.

1) If the input AC voltage is high (resulting in high DC voltage) why would moving the input tap to a lower setting make the DC voltage lower? I would have thought by moving to higher tap setting you would be incrementally "stepping down" the input to the bridge rectifier. The taps (74,75,76) are already in the highest position.

2) I understand that it may be difficult to get an accurate reading from a DVM on a RPC until it is loaded. Would this also apply to a Phase Perfect digital phase converter?

3) Is there any chance of damaging the machine if you start the servos with the DC voltage outside (you mentioned 368v below) Haas's recommended range?

Thanks again for your time.

-Brian

[Donkey Hotey]

I really can't comment on how the Phase Perfect would respond. I know that I had to learn a lot about my own RPC and the incoming voltage when I had a Vector Drive die with very low hours. I literally spent hours with a dual-trace oscilloscope looking at every aspect of the power in that machine, in addition to researching it on the web.

What I learned is that no RPC is a perfect solution. The best solution is a solid-state, three-phase inverter drive--but that's pricey as heck and probably not necessary.

Phase Perfect seems to have a good reputation. I'm not sure if I believe in their claims but I'm not in that business so maybe they've got something in their boxes other than carefully chosen capacitors and a three phase motor.

Originally Posted by bbrown01 I would have thought by moving to higher tap setting you would be incrementally "stepping down" the input to the bridge rectifier. The taps (74,75,76) are already in the highest position.

Yes: I agree with you. I might have miscommunicated. By "lower taps" I meant higher number on the labels but lower actual output voltage. You're outside the voltage range but the transformer is already tapped at the highest numbered terminals?

I'm wondering if Haas might have crossed some wires installing the transformer or if somebody at the transformer company screwed up and the whole thing is tapped incorrectly.

Originally Posted by bbrown01 3) Is there any chance of damaging the machine if you start the servos with the DC voltage outside (you mentioned 368v below) Haas's recommended range?

I'm not Haas. If it's their machine, they have to take care of it. I can tell you this: the machine has high voltage alarms. If it thinks that the input is really high, it will actually start beeping at the control and do a 15 second countdown before shutting itself off. It will also give low voltage alarms. It's pretty good about monitoring itself.

The techs have a range that the voltage is supposed to be within but something else is fishy here. Your incoming single-phase power is two 120V legs? 120V sounds a little high but should be within the range of the machine. Mine is usually between 115-117V but dips down to 110V occasionally.

[bbrown01]

>The best solution is a solid-state, three-phase inverter drive....

>Phase Perfect seems to have a good reputation....

Phase Perfect is a completely solid state device controlled by a DSP. They don't use any motors. They guarantee the 3-phase voltages to be within 1% through the entire load range. And yes they are expensive.

>You're outside the voltage range but the transformer is already tapped at the highest numbered terminals?

Yes. The taps are in the left most position and the DC voltage is 384v. I suppose it's possible that the transformer was wired incorrectly at the factory, but I don't want to be the one to damage something by moving the taps to a lower position and testing the voltages.

>Your incoming single-phase power is two 120V legs?

Yes. Mine are more like 124V each.

[Donkey Hotey]

Ahh..I was thinking of Phase-A-Matic, not Phase Perfect. I stand corrected.

(deleted)

I have two Haas machines and both had electrical problems. The VF-2 had a Vector Drive that died from an infant mortality problem on its logic board (I had it narrowed to the circuit but couldn't repair it). Some might have blamed it on the RPC but it didn't explain the TL-1.

It seems the TL-1 had a problem with its DC power supply from the day it was delivered. It would blow the panel breakers almost every time I tried to start it. I thought it was over-sensitive breakers. Of course Haas was suspicious of the wiring and the panel, not the machine.

I can't blame them--the stuff is supposed to be tested at the factory, inspected and signed off. After 4 months, the power supply finally let go with a spectacular 'pop' from inside the cabinet. That noise and the burned circuit-board-smell narrowed the problem down for them. A circuit trace from the terminal block to one leg of the rectifier blew right off the board (about 1/4" wide, high-current trace).

After replacement, the machine has been a joy to own. It starts every time and has never had another problem. Ironically, the machine showed up with hundreds of 'on hours' already on the clock. If it was going to die, it should have done it already. It didn't.

And I know a guy with a big horizontal (can't remember the model) but it had some kind of power problem where it would just error out randomly in the middle of a part cycle. They had numerous techs look at it, engineers from the factory, monitored his incoming power with a data recorder, etc, etc.

The salesman just happened to be talking to one of the guys at the factory one day (after a few months of frustration) and mentioned the problem. He had them modify some obscure variable that nobody thought of and the problem never came back again.

So Haas has every reason to think that their machine should be good when it arrives...but I'm here to tell you that they can have problems right off the truck. If the machine is designed to handle 240V and you have 240V then the transformer should work. If it doesn't, something has to be wrong with it (or the measurement methods--not likely but???).

Edit:
I had it bass-ackward. From memory, I thought the taps were all live. I just went out and looked at my VF-2. I was wrong...never mind with that idea of measuring at different taps.

Interestingly though, mine is connected to the highest voltage taps and I've got 115V legs. I turned the machine on and the displayed bus voltage is 331-332V. If my input voltage were based on 120V legs, that would be 4% higher. That would be about 346VDC. I think you're in the ballpark.

[bbrown01]

Thanks for your help Donkey.

I'm not sure what to do at this point. The HFO tech won't come back out until either the DC buss reads 360v or less or all three legs of the 3-phase are well within the range of the machine specs. I see I have one of 2 choices:

1) Install a buck/boost transformer (e.g. 12/24 or 16/32) and drop the incoming single phase voltage down hoping that this will calm down the manufactured leg of the RPC. That's an additional $750 plus electrician.

2) Replace the RPC with Phase Perfect knowing the PP with be within 1% of the incoming voltage (248VAC).

[PBMW]

I own three phase perfects. I wouldn't think of doing it any other way. Dead reliable. Cleaner power than the power company delivers.

[Donkey Hotey]

Have you personally read the Haas installation manual?

http://www.haascnc.com/customer_serv...stallation.pdf

These are right out of the book:

The maximum leg-to-leg or leg-to-ground voltage should not exceed 260 volts, or 504 volts for high-voltage machines with the Internal High Voltage Option.

Use a digital voltmeter and appropriate safety procedures, to measure the voltage between all three pair phases at the main circuit breaker and write down the readings. The voltage must be between 195 and 260 volts (360 and 480 volts for high-voltage option).

You're good there.

Bottom line: you're within their supply specification. There is something wrong with that transformer or how its wired. It's their problem.

Ahh...I just looked up your HFO. You're dealing with Selway? Play hardball buddy. From everything I've read online, you aren't going to get any love from them. They sound terrible to deal with. I'm sorry. Really. Your experience with the Haas brand will not be the same as others on here. This BS is probably just the beginning. You can be nice but only to a point. Call the factory yourself if you have to. I'm sure they hate know-it-all customers but in some cases, you have to become the expert.

[bbrown01]

Hi Donkey. Yes I have read (many times) the installation guide. That's where I'm quoting most of my information from. I may or may not be in spec. With my meter, I'm in spec. With the HFO tech's true-RMS meter I'm not. And that's what he's going by.

I've decided I'm not going to mess around with RPC's anymore. I ordered a Phase Perfect. They're shipping it Monday.

PBMW, I'm glad the Phase Perfect is working out for you.

I'll let you know how everything works out.

Thanks again for all your help.