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Step down 50 volts

I am going to Teds shop today about noon.

What specifically should I measure.

Line voltage
Voltage in to machine
Voltage in for 2:1 transformer
Voltage out for 2:1 transformer
Voltage is for stepper driver
Not sure how to get voltage out for stepper driver - as that is not constant
Voltage in to stepper motors - not easy to get to because of sheet metal guarding

As to design specs on the machine.
This is a Chinese machine. Documentation is pretty close to ZERO as well as tech support
The 2:1 transformer has 220in and 110 out (
 
OK - I did some testing

Wall plug is 245 volts
In to machine is 245 volts
IN - to the 2:1 transformer is 245 volts
OUT - from 2:1 transformer is 125-126 volts
IN - to Stepper Driver is 125-126 volts

Stepper Driver requirement is 60 - 110 volts

The steppers are being overpowered.

How do I get the steppers into mid range for required voltage.
 

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My opinion is still that you should try dropping the line voltage, I say that because if I read it correctly, the spec'd input voltage is 220vac. If you drop your 245 by 10% you should be almost right on at the spec'd input to the machine (22-VAC). If it's designed to work at 220VAC, then your spindle speeds should also be correct (just my opinion).

Another way to test this is to put out the word among fellow hobbyists that you'd like to borrow a BIG variac, something like a General W10 or W20. These are industrial variable AC transformers designed to do exactly what you are looking for .... but are variable. The W10 is 10 amps and the W20 is ... yup, 20 amps. :)

I have both here, and they can often be found at electronic flea markets for under $100 in perfect working shape.
 
I looked at a Variac but As Darren pointed out it may not be a good long term solution.

Also getting real 220v IN to the transformer only gets me to the max input or higher going IN to the stepper drivers.
As measured the 2:1 transformer output is more than 50% of the input and still overpowers the stepper drivers

If I use a buck transformer 240-208 I get closer but still not in mid range for the stepper drivers and I am concerned about the VFD.
The BOB is powered thru a 220-24 volt power supply, but I can adjust that one a little bit with the adjustment screw

If I can get down to 190 IN for the transformer that would be better.
I can do that with a Variac, but still concerned about longevity.

To save money - the variac may be the way to go.
Everything I see to get the voltage we need at the VA of 2000 is around $1000 more or less.
I had Larson quote a 240 - 95 transformer and it was a little more that $1000
 
Leo Voisine said:
I looked at a Variac but As Darren pointed out it may not be a good long term solution.
Click to expand...
Nope, it wouldn't be and I wouldn't use it for that .... just borrow one for testing ... kind of like a proof of concept. Then you can get real time voltage and current numbers, in operation. You have a clamp on meter ?
 
Don Baer said:
Just a thought Leo but has he called the electric supplier and see if they can change the taps on the transformer supplying him power ?
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He called me. There is no other place or person to call. Just me. There is no electric supplier. His business partner bought a buck 240-220 from Larson, but I told them to return it as that would not solve the problem.
 
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John Bartley said:
Nope, it wouldn't be and I wouldn't use it for that .... just borrow one for testing ... kind of like a proof of concept. Then you can get real time voltage and current numbers, in operation. You have a clamp on meter ?
Click to expand...
ahhhh yes. That WOULD give me a much better sense of concept.

Clamp on meter - as in a test meter to clamp around the wire for amperage testing. Yes I just bought one just for this. Never used one before, but I can learn.

I like the Variac aproach. I will find one that is not too expensive, and maybe he will buy it for me for testing. I do like that idea.
 
Leo Voisine said:
There is no other place or person to call.
Click to expand...
Does he make his own electricity ??? if not who does he pay the electric bill to they should be able to do something IF the voltage is too high. If the supplier is causing appliances to go out from over voltage I would think they would change the taps on the pole. Utility companies use high voltage usually. "Utilities typically run primary distribution voltages between 7,200 and 34,000 volts (7.2 kV – 34 kV) to neighborhood transformers. Common North American voltages include 7,200/12,470V or 13,200V, while newer, higher-capacity systems may operate at 34kV," this is what I am talking about. They step it down before supplying the end customer.
 
Leo Voisine said:
Don, I didn't understand your question.

I went to Teds shop and tested the voltage as I posted above.

It is within the 240+/- 5%
I measured 245 volts

I thought you had read that post above, so I didn't understand what you were asking.
Click to expand...
I think part of what he is saying is to ask Ted to call his utility company and ask them to come verify the feed to the house is within spec. My daughters house recently was blowing fuses on their furnace and lights were flickering and dimming often (during non-heavy loads). Turns out there was a over voltage issue and they repaired it.

I don't think that is the issue with this machine, but certainly could contribute with having even higher voltages than it would normally have.
 
Not sure. When I said 260 volts, I was wrong I was talking from memory of something I did mmmmmm maybe 1/2 to 3/4 of a year ago.

You guys promoted me to verify my readings, which I did and posted here.

I do understand what you and Don are saying. There may have been a glitch in the power grid and it was fixed.
Absolutely.

However, I am pretty sure it was all about me saying that I measured 260 volts.
ALL of that confusion is on me --- sorry. My brain glitched.

Sooo - Today - we are on 245 volts coming into the building.

Either way, Teds stepper motor drivers are still being overpowered.

John is going down a path that is on target to my issue
 
Leo Voisine said:
Not sure. When I said 260 volts, I was wrong I was talking from memory of something I did mmmmmm maybe 1/2 to 3/4 of a year ago.
Click to expand...

I'm wondering if you're overly discounting your memory here and it did have 260v at one time. That would certainly be concerningly high and possibly could have nuked the steppers if it had happened. I'm not sure what would cause that either.

I do realize that the 245v leaves you a bit out of spec for the steppers still.. but if he had had a super high voltage event - especially sustained in the past that would've been a lot worse. IDK.. just a thought (I know I've thought I was wrong when I was right before.. and have been more than guilty of not good notes in the past - and probably will be again in the future..).
 
Ryan Mooney said:
I'm wondering if you're overly discounting your memory here and it did have 260v at one time. That would certainly be concerningly high and possibly could have nuked the steppers if it had happened. I'm not sure what would cause that either.

I do realize that the 245v leaves you a bit out of spec for the steppers still.. but if he had had a super high voltage event - especially sustained in the past that would've been a lot worse. IDK.. just a thought (I know I've thought I was wrong when I was right before.. and have been more than guilty of not good notes in the past - and probably will be again in the future..).
Click to expand...
Possibly - but I really don't think that history of the voltage is the issue. I think I may have said it is around 130 going into the stepper motor drivers.

I have a retired electrical engineering friend that I spoke to about this issue. It is a VVVVVVEEEEEEEERRRRRRRYYYYY VVVVVVEEEEEEEERRRRRRRYYYYY VVVVVVEEEEEEEERRRRRRRYYYYY ---- LONG conversation with him, that end with talking about his steam engines and the railroad club - that again become another very very very long conversation. He is extremely knowledgable about this stuff. To him it is basic elementary stuff. He is not in the least willing to get into it with me and not at all willing to come look at it. Last time I talked with him about anything was 4-5 years ago. I see him once in a while. We DID get some conversation in about this issue and he DID completely and fully understand. He said the stepper driver would be able to withstand variations and a lot of issues - but not overpowering. I do NOT want to go back to him for advice.

He was telling me that I could built a transformer that would take my line voltage and drop it down to the required input voltage. Just a note here ----- The 220v on the top of the 2:1 transformer is NOT the design voltage for the machine, it is simply to state that it is a drop down voltage on THAT one single transformer. I can input 250, or 190 to that and get something like a 50% step down. In order to get the 190v that I am targeting a buck is not the answer, so - what is the answer?

What is going into the stepper motor drivers - today - is the issue I am trying to get to.

I really really don't think the power company blew the stepper drivers. That entire conversation is based on my poor memory.


Option 1
Lower the voltage going into the 2:1 transformer to about 170 - 190 volts.
This will give me the between 85 - 95 volts for the stepper motor drivers
(the transformer is not truly a 50% step down - see my measurements above)
Amperage going to stepper motors are restricted to 4.5 amps
This stays within the VA of 2000
Cons - Does not allow me to increase amperage going to my stepper motors to 6 amps
(I did make a post about this above)

Option 2
Replace the 2:1 transformer with one that can transform 245 volts to 85-95 volts with 4 taps and 3000 va
That would give me the correct voltage to the stepper motor drivers AND to increase the amperage going to the stepper motors.
Cons - price

What Tony posted can be a viable solution, but I don't know where to find the correct one.
245 - 250 volts IN
85-95 volts OUT
4 taps out
Rated at 3000 va (so that I can increase amperage going to the stepper motors.)

John suggested a variac to test the concept
 
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