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This may be a bit weird but I am gonna ask anyway

Leo Voisine

Leo Voisine

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6,281
Location
East Freeetown, Massachusetts
I have a client with a Chinese machine VERY VERY similar to my chinese machine

We just needed to replace all 4 Yako 2811 ma stepper motor drives in his machine
I have the same steppre motor drives in my machine - but my machine is 2-3 years older

The power supply on my machine measures 104 vilts going to the stepper drives

My clients machine measures 124 volts going to the stepper drives

On the YAKO website the recommended voltage max is 90-110v a/c - but it also states max of 130v

I think 130v is over voltage

Is there a way to reduce the voltage output of the power supply that is going to the stepper drives
 
I wouldn't be surprised if there was a potentiometer on the power supply in which case it would be as simple as turning the dial a very very small amount.

It might be interesting to also measure the input voltage and see if he's running super hot at the wall.
 
I have a pic on my cell phone. I don't see a pot. I don't see anything on the web site either. I do have other power supplies and yet "THEY" do have adjustment.

2000VA Single Phase Power Transformer

JBK5 series transformers are used in the 50-60HZ ac circuit of input voltage less than 660V and output voltage less than 230V as machine equipment in various area for controlling the power of electrical equipment , lighting and Signal lamp. This series transformer is adopted in Germany technic...
www.reelenelectric.com

I got an answer back from the company.

Dear Leo,

If you need 100-105V output, you need change a new transformer.

Thanks & Best Regards,
Henry Zhou
 
Looks like that is just a transformer. You might verify that his is connected to the same winding as yours for the 110v leg of it vs the 127v one. You may have to take it to a shop and have the windings checked, they could shorten or lengthen it possible to correct the voltage. Also what Ryan said about input voltage to make sure his isn't reading high for some reason from the panel/utility service. The transformer is going to output a relative voltage to the input.

A replacement might be needed though. That does appear to be an AC output also, which you might verify when shopping.

Edit: corrected voltages
 
OK - I am pretty sure I have this nailed down.

The power supply in the machine is --------- 220v input 110v output.
it is 2KVA or 2000VA

I measured the input voltage at 238V and out put ay 124v

I am pretty sure the 238v input is causing the high 124v output

The stepper motor drivers have a max input voltage of 110v

The 124v is over voltage

I need to reduce the 238v coming out of the outlet in the wall down to 220v or a little lower.

We have a 30 amp circuit breaker in the panel

I am not sure what it means 2000VA on the power supply ---- 9 amps?
2000 / 220v = 9

Sooooooo - do I need a 240v to 220v stepdown transformer rated for 9 amps
 
Commercial power in the U.S. hasn't been 110/220 for a long time. It's now 120/240, so what you're reading at the outlet is correct within limits.
If your machine's power supply is that sensitive, then you'll need some sort of a voltage regulator. Perhaps a UPS rated for 220 output?
 
Sounds like you need a different transformer with a lower output or different steppers with higher voltage then. There may be come circuits to step down the voltage also, but someone else may need to speak to that.
 
As I go thru this process of figuring out about this stuff I am learning a lot of stuff, like what is 220 voltage.

It apears that US 220 is not the same as the rest of the world 220. I am not smart enough to completely understand all this stuff so to convey what I have found may not sound right.

In the rest of the world 220 is single phase and is generated to be 220. In the US 220 comes together as two 110v lines. Don't ask, I really don't understand it.

Also, in the US as Jim said we don't have 220. What we have is 240.

My clients machine just blew all 4 yako 2811ma stepper motor drivers and we replaced them. They are rated for 90v to 110v.

The power supply from the outlet is supposed to be 220v. In the rest of the world - sure - no problem, but here in the US we are smater than that, we have our goofy 240v.

So the Chinese power supply wants 220v input so it can convert to 110v to supply the stepper motor drivers.
In reality the input is 238v and the output is 124v

I think the stepper motor drivers blew because the power supply was outputting 124v "because" the input is 240 and not 220v.

In MY machine the power supply is different. I also have 240v in, but the output is 104v. It is supposed to be 90v, but is within the 90v - 110v on the stepper motot driver.

I have the same stepper motor drivers that are rated for 90v - 110v input.

My machine is 2 years older and I have never had a problem

My suspecion is that the stepper motor drivers in my clients machine failed because of the over voltage.
Granted the client machine is 8 years old. Mine is 10 years old with no issue.

I can buy a new transformer, power supply, or whatever. My problem is that I don't know enough to be able to spec out what I need to fix the issue.
I know I can fond a transformer to take 240 down to 120 - that is easy. I need to take 240 down to 220, BUT I need to make sure I have the correct amperage, and I don't want to spend $500 or $1000 to do it. We just spend close to $1000 on the drivers.

I know an electrical engineer from my past that I may tap into. If I was still working I would just go see Bob in electrical engineering and he would know. BUT I can't do that.
 
Well, also have to consider that the 220v is at 50hz in other countries, vs 240v 60hz here, which has some affect on the transformers output as well.

It might be worth taking the existing transformer to a shop that does motor windings and transformers to see if they can modify it by either adding/reducing the windings to get the correct output voltage.

Per google, so take with a grain of salt, but might be a option...
How removing windings affects voltage
  • Removing secondary windings reduces voltage. If you remove turns from the output (secondary) winding, the secondary voltage will decrease relative to the input voltage. This is the principle behind a step-down transformer, which has fewer turns on its secondary coil than its primary.
  • Removing primary windings increases voltage. Removing turns from the input (primary) winding will increase the voltage on the output (secondary) side. This changes the turns ratio, making the transformer behave more like a step-up transformer, which has more turns on its secondary coil than its primary.
 
Leo Voisine said:
In the rest of the world 220 is single phase and is generated to be 220. In the US 220 comes together as two 110v lines. Don't ask, I really don't understand it.
Click to expand...

It's actually really simple.... in concept at least.. :D

There's some was here... there's also some that use solid state foo now but lets stick with the easy version and yes I'm simplifying somewhat don't come at me... Anyway..

The way the high voltage from the power company is converted into low voltage 240v is there is basically a coil that is on the high voltage side and a coil on the low voltage side. Induction transfers power between them and the ratio of the number of coils on the high side vs the low side determines the voltage drop. The coils are sized for whatever the expected output voltage is in relation to the expected input voltage.

The two "hot" legs have a 240v (nominal) differential and are tapped at the top and bottom of the low side coil. In the US there's another tap in the center of the low side coil (the "neutral").. which means there are half as many windings between it and each end.. and thus half the voltage between that neutral tap and either leg or 120v.

This is relevant because the 240/220->100/110v transformer works the same way. Automation direct has a nice explanation with pretty pictures as well: https://cdn.automationdirect.com/st...-pdf/TX-Transformers-and-Filters-Overview.pdf

To your amps question, yes ignoring power factor .. 2000 / 220v = roughly 9amps. I'm ignoring power factor but it would be useful to sum up all of the expected loads and check that because you might actually be drawing more than 9 amps (at a PF of 40% which isn't unbelievable more like 22a...). Using a ammeter to measure real load might be useful..

Whether that's sufficient depends on where you put it..

I believe the JBK5-2000VA you referenced above is ONLY feeding the 100v steppers? In that case you need like 10a for the transformer unit if you replace that or put the 240v-220v transformer immediately before that step down transformer. You have the option of just replacing that OR putting a 240-220v transformer in front of the whole machine (which might? make some other components that want 220v happier.. maybe.. I mean nothing else has exploded yet..) in which case you'd need something to accommodate the draw for the whole machine (assuming the spindle, etc.. is also driven off of that? I have no idea how this is actually wired..). Putting a step down transformer before the steppers is likely by far the cheapest solution...

Something like https://www.larsonelectronics.com/p...40v-primary-220v-secondary-22-94-amps-50-60hz would probably work and has more than enough slop in capacity for there being any power factor issues.

Darrens point on the 50hz vs 60hz is also worth considering. Things designed to run at 50hz run faster and maybe a little hotter at 60hz.. which could plausibly lead to earlier failure as well.

Ditto on the suggestion to see if you can get the existing adjusted..the docs on the JBK5 series are thin.. but I found one that suggested some of them offer a -5% tap point which would put your output at 114v.. IF the one you have offers that (not all do? I don't think? ) it might just be as easy as moving a connector inside the case.. (that's probably wishful thinking.. but they are pretty simple devices).
 
all good and useful info I have not yet looked at your links, but I will look

The spindle is 220v as well, so I would think a step down "something" from 240 to 220 would be beneficial overall.
YES - the JBK5 is feeding ONLY the steppers

If I could find that "something" to step down the 240 to 220 at the amperage to satisfy the machines needs ( I am thinking 30 amps) I could just step down the 240 from the wall and input 220v to the main connection in the machine. I know we have the machine on a 30 amp circuit breaker in the breaker box. So, I think - but not sure - that I need something capable of 30 amps, but maybe 10 amps is ok, Not sure. The spindle is 220v as well. Not sure of the wattage but it is either 3 or 4 HP. There is a calc for that conversion.

I am not sure - but in order to measure amperage the machine would need to be running on all 3 axis's with spindle running and under a load - cutting somewhat heavily. Even so - I don't know how to measure the amperage.

On the existing JBK5 - there is nothing adjustable, unless the windings are added or removed. Definately not in my pay grade.
 
As I am learning about this stuff one more point that may be of significance

Both my machine and my clients machine have a toroidal power supply.
the JBK5 is a toroidal unit

Is what I am calling a power supply the same thing as a transformer?
 
Yeah I saw stuff like that but it looks intimidating to me. I am not afraid to try it. If it does not work for my client machine it would become just another part for my CNC lathe that I want to build some day.

I didn't think about 4 individual versions.
 
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