Chiller compressor

[SmoothArc]

Hey everybody. We have an interesting and very frustrating problem with the water chiller for our cnc laser. When the compressor kicks in it is drawing current seemingly from the entire machine. The main problem is that this is drawing on the High voltage power supply for the laser resonator. When this happens it can lead to problems cutting since the beam power dips for a brief moment when the compressor starts. It's certainly understandable when the lights in your house flicker when a load is applied but this is an annoying problem for a piece of equipment. Here is what I can tell you. The compressor was recently replaced as the old one was deemed bad. This did not change anything. Main power coming into the machine is fine. The amperage draw on the compressor was said to be fine. I have swapped out the main transformer with a spare and that didn't help either. One thing I found odd is that I get ten volts running through each wire going to the compressor when it's not even on. This is after the contactor where there should be no voltage. Sorry if I haven't provided enough info and thanks for your time.

 

[3DDave]

10 volts relative to what exactly?

 

[itsmoked]

Many questions. Some suggestions.

The 10Volts matters not. It's capacitively coupled nothing, that you see only because modern meters have such high input resistance.

Is this machine rated 230 or 240V and you're running it on 208V? If so you need a transformer or transformers to get the voltage up to 230/240V.

You say "main transformer", what EXACTLY does this transformer run? The entire facility? Just the machine?

What rating is the this transformer? 10kVA? 30kVA? What kVA?

What does the machine placard state for power requirements of this machine?

You can photo it and post it in-line in here using the feature:

Typically there is also a plate on the chiller unit also. What is it's rating? A picture of it would be good also.

Has the machine ever run without the chiller causing this issue?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[3DDave]

(I'm betting it's got a 50 foot extension cord involved somewhere. Also, don't make fun of my meter. I wound the movement myself from lamp cord. The movement has roller skate bearings. Not those fancy in-line bearings - reliable pressed steel races.)

 

[SmoothArc]

3ddave
The ten volts comes from touching one probe to the compressor wire and the other to the chillers chassis.

Itsmoked
I will gather as much info as I can today. I apologize for leaving such vague information. The transformer I was referring to is the main transformer supplied with the machine that the incoming power runs through. We have spare parts so I thought I would replace it.

Thanks for the replies

 

[jraef]

the compressor is not "drawing power from the laser", that's not how things work with electricity. What is more likely is that the SOURCE of your power is insufficient to handle the "starting current" of the compressor, and that causes a momentary voltage drop. The voltage drop then affects the power supply for the laser and it shuts down to protect itself from an under voltage condition. That would not at all be unusual.

The comment regarding the 50' extension cord is based on the notion that having too long of a wire run from the source of your power to the machine is contributing to the voltage drop when the compressor starts, a very valid concern. It could also be a number of other factors or combination thereof. If you post details of the equipment and installation, such as the compressor motor nameplate details, the size of the circuit feeding the machine, any extension cords, etc., we may be able to further help diagnose it from afar. Or better yet, get someone local to come in and take a look at it, preferably someone with experience in large machinery installation.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[SmoothArc]

I overlooked looked the 50 foot extension cord comment. There is only about a 15 foot run to the chiller. I'm not sure what size wire off the top of my head. Anyways, we have had a local Hvac and machine repair company take a look at the problem and no one seems to know. I have spoken to the mazak and they weren't much help either. Although I have been running this laser for years now I can't confirm that this problem didn't always exist. We didn't always do the type of cutting we do now that gives us problems. (Cutting with nitrogen is less forgiving to changing variables in parameters).

Here's what I came up with today. I'll attach a the few pics I have also.

The chiller has no nameplate on the outside for specs. I will try to get a panel off and get the compressor info tomorrow.

It seems we have 240 volt 3 ph (200 amp) service coming in the shop. Thats what the breaker panel says anyways. This was deemed okay when tested. What might be interesting to note is that there is a transformer (I think) outside our shop that I was told is just for our laser. It is enclosed right now so I dont have any specs. I will see what I can find out tomorrow as well.

Here is the tag from the electrical cabinet

This is the main transformer for the laser.

And here are a few wiring diagrams for the main power circuit.

I see the transformer can be tapped for 210,200 and 190 volts and is currently on 200. What's the reason for the three options? It appears it is also tapped correct for the 240 volts incoming.

 

[3DDave]

The lights in a house dim because the lines from the pole** have enough resistance that the high current draw shifts part of the available voltage to a voltage drop in the wiring. The typical homeowner is most likely to see this in undersized extension cords.

In this case that drop could be (for example) from the pole to the main distribution box, from the box to the place this is wired, the wiring immediately to the machine, and/or between the transformer to the individual components.

I expect an electrician could measure the voltage drop between each connection for the components inside the machine to see where the biggest drop. At the least I would see about cleaning all the connections and checking to see that all the wires are in good shape and have not developed internal fractures. An IR camera might also help to find any high-resistance connections.

**Or, if the items are on the same circuit, that the wiring of that circuit is providing the resistance.

 

[jraef]

200V is a common voltage in Japan, that's why.

From the looks of it in the first drawing, they use 200V for everything "domestic" which for them means Japan. Then for "Export" (second drawing), they add a 45kVA transformer to power the laser with 480V, but the chiller is still getting 200V, out of different taps of the SAME transformer. In the first drawing though, they show that a 1500W laser, as you appear to have, requires a 45kVA transformer. But in the second drawing, they are apparently using the SAME transformer, still rated 45kVA, but it is now ALSO having to supply the chiller. Nothing indicates the size of that chiller motor, but since that is the size transformer for the laser ALONE, my immediate suspicion is that the transformer is inadequately sized to handle the added burden of starting the chiller when the laser is running.

But... you say it's been working fine for years? Was the laser being used at a lower power setting then and now you are using it at full power? That would explain why it may have worked up until now. That's my theory #1.

Another possibility (theory #2): 200V motors are not common here in the US and EXTREMELY rare everywhere else (except Japan of course). So might someone have substituted a 230V motor, thinking "close enough"? So that scenario would go like this: original chiller had a 200V motor and worked fine for year, but eventually the motor wore out. You had someone replace it (HVAC company?) who was unfamiliar with the fact that Japan uses 200V and ASSumed that a readily available "tri-rated" motor here in the US, meaning rated 208-230 / 460V, would be "close enough". But it is not; a tri-rated motor design is actually taking a 230V motor and designing in a slightly higher tolerance to accept 208V, but NOT all the way down to 200V, at least not without consequences. One of those consequences would be higher than normal starting current. So the first motor worked as designed, but wore out, then the replacement was not the right fit and is giving you new problems.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[3DDave]

I note that this is likely an old machine - is it possible that smoothing capacitors in the laser control module are in need o replacement?

 

[waross]

Are you sure that you have 240 Volts incoming?
240 Volts three phase is a valid North American voltage but 208 Volts three phase is about 1000 times more common.
240 Volt taps with a 208 Volt supply will be a problem. This is worth checking.
I see a 45 KVA transformer.
At 240 Volts that will be 108 Amps. That tracks with the 150 Amp breaker.
Transformer feeder ampacities are sized at 125% of the transformer, that makes 135 Amp rated cable.
For flexible cord that will be 2/0 AWG. That's a very large cord.

What to do?
Check the voltage at the transformer secondary while the motor is starting.
Check the voltage at the transformer primary while the motor is starting.
The diagrams are interesting but don't help a lot. The problem is probably outside the machine.
Is your plant supplied with 480 Volts?
Pictures of all transformer nameplates will help.
A picture of the motor nameplate will help.
You ha a bad voltage drop somewhere between the street and the laser control unit.
It is difficult for us to help find the problem when we have no information about the wiring and transformers between the street and the laser control unit.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[waross]

Hi Jeff

In the first drawing though, they show that a 1500W laser, as you appear to have, requires a 45kVA transformer.

Could it be that the transformer is sized to the size of chiller required for a 1500 W laser?
3D² 'Failing smoothing capacitors in the laser power supplies.' Good call. This may be worth checking.
I remember a department store where the power supply capacitors in the POS terminals would hold up long enough for the standby generator to come online. I imagine that when the caps age they would be dropping programs before the standby sets kicked in.
This could be an issue here if this is a new machine.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[SmoothArc]

Jraef

The problem only became apparent when we started using nitrogen as an assist gas. When oxygen is being used and there is a small dip in power you would barely notice thanks to the thermal reaction taking place. When nitrogen is being used a change in power will result in losing the cut completely. Therefore I can't say that this hasn't been occuring from day one. Also I'm not aware of the motor ever being replaced before my time so I dont know if the old one was the original. I could certainly see how someone might just replace what was there with a motor of the same specs when it wasn't right to begin with.

Waross
I thought the 240 was odd as well. I always thought 208 was the norm. I'm quite positive we dont have 480 coming into the shop.

Thanks again to all. I'll regroup and see if I can gather more info on all the voltage and grab some more pics.

 

[edison123]

The laser transformer seems to have many taps. Why not change it to next higher voltage if voltage drop is indeed the issue with the laser output?

Muthu

http://www.edison.co.in

 

[davidbeach]

Move the chiller connection to the source side of the laser transformer, even it that means also adding a second transformer. That or replace the transformer with a (much) larger one.

Or, change the chiller controls so that it starts before the cutting operation and continues running until after the completion of the cut. That changes it from an electrical problem to a thermal problem, but if it becomes a thermal problem you just need a heater to keep the chiller busy if the laser isn't producing enough heat.

 

[waross]

I would suggest finding out where the problem is before making any changes.
For instance:
If the problem is mainly in the transformer, add a smaller transformer to power the laser module.
If the problem is a weak supply or a feeder cable that is undersized, changing transformers may not help.

Or, change the chiller controls so that it starts before the cutting operation and continues running until after the completion of the cut. That changes it from an electrical problem to a thermal problem, but if it becomes a thermal problem you just need a heater to keep the chiller busy if the laser isn't producing enough heat.

That may be the solution.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[edison123]

Or a 2 KW quick acting voltage servo stabilizer just for the laser unit?

Muthu

http://www.edison.co.in

 

[itsmoked]

Does the chiller start-stop during cuts or does it typically not start until a cut has proceeded for some time period? Once it starts does it ever stop during cutting?



Keith Cress
kcress -

http://www.flaminsystems.com

 

[SmoothArc]

Sorry guys I was quite busy friday and didn't manage to dig into the the machine. Thanks for all the advice so far.

One thing I can mention is that the chiller cycles on and off throughout the day. Cutting will make it cycle faster. So it does turn on and off while cutting parts.

Hopefully I'll get some more info in the next couple days. Again, thanks for all the replies I didn't expect as many responses as I have been getting!