Question for those running a KBAC 27D.

Chris Railey

Chris Railey

Well-Known Member
What is your boost pentameter set at? If it were a clock where do you have it set? I am wondering if I had my boost set too high and that is what caused my 27D to fry again. The tech support people said it looked like over-voltage caused it. We all know for now, I only have a 60 amp service to run my house including the shop so I was trying to figure this out.
 
My first question is why you only have 60A service? Is your box, wiring, etc. in good shape? I think I mentioned the first time you had issues it sounded like you might be losing a leg/voltage imbalance across the legs. I will reiterate that now. Power supply issues are the #1 killer of electronic control systems in my everyday world. It's almost never the equipment. Inspect and meter everything before you move forward.

Here is mine. I don't think I adjusted this one at all. As I recall, they have a little "if it does this, adjust this" type set up guide. In the book or online.
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I have 60 amp because that is what my house was built with. I will have a sub panel and 100 amps in the shop soon. My boost, for some reason was set to at least 50%. I think I remember reading that could cause troubles but I could not remember if the motor or drive was at risk.
 
I also run a 27D, but in my case it's on 115v input voltage. A couple of thoughts:
- I didn't change the Boost Voltage adjustment as it came from the factory. Even after re-reading the KBAC manual, I don't see a reason to adjust this feature. I'd say leave it at the 9 O'clock position, as it came from the factory.
- Take a look at whether you have your 220v input to your 27D to see if it is connected to a GFCI breaker. These KBAC units don't play well with ground fault breakers. I found that out on a 24D I have on another machine. A lot of newer houses will have GFCI breakers on all circuits built into the service panel.
- If you are adding another breaker panel (100 amp) and that is a sub panel served by your 60 amp panel, it won't really help your load carrying capacity. You'll still be limited to an overall 60 amp service based on the rating of your primary panel. Sure, you can add more breakers in the 100 amp subpanel, but that doesn't increase the capacity of the incoming service. I am not a licensed electrician (any more), so check with a local electrician to review this question, and compliance with local codes.
- Get a digital volt meter and check the 220 voltage that you are connecting to the KBAC unit. Check across the hot legs and across each of the legs to neutral. Typically, the voltages you see at your KBAC unit shouldn't vary more than +/-5%.
- With the events you've had I would be suspicious of how your overall house load is affecting voltage to your grinder. Try this: with a digital volt meter connected to your 220v supply at the grinder, turn on each high load device you have in your house, including Electric Range, Electric Water Heater, Electric Heaters, etc. Anything that has a high load - turn them on individually then combined. If you see a large drop in the incoming voltage at the grinder you might have identified the problem. The solution is likely to increase the wire size feeding the high load devices in your house and grinder. Again, check with an electrician.
- Also keep in mind that not all incoming electric services to a residence are the same. You can have a "dirty" line that has large frequency variations, voltage fluxuations, or other line harmonics problems created by adjacent electric customers. These issues are much harder to identify and correct.
Hope this helps.

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Chris Railey said:
I have 60 amp because that is what my house was built with. I will have a sub panel and 100 amps in the shop soon. My boost, for some reason was set to at least 50%. I think I remember reading that could cause troubles but I could not remember if the motor or drive was at risk.
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I dont know what your local electric codes allow but if you can confirm the size of the Service Entrance Cable you may be able to change the meter socket and panel. Many of the 60A services used Copper wire and depending on size and code restrictions you might be able to do that? Ask your electrician.
 
A few years ago the big ice storm tore the mast off of my house. When it was fixed a 200 amp service was added outside but the inside panel was not upgraded. The wall I am going to add the sub-panel to is on the opposite side of the wall my feed comes to the house. So the sub-panel will be “fed” correctly. I have always thought that too low voltage is burning it up. That is why I am running it off of my inverter generator until I get my sub panel. Once I get my sub panel done I think I will switch my grinder over to 220v. I run currently on 115 too. So when I put the sub in should I not use GFCI breakers at all or just on the circuit for the grinder?
 
Just my 2 cents. I've been using the KBAC controllers ever since they became commercially available. The only trim pot adjustments that I have ever had to make were the "Min" and "Max". I did learn early on, the hard way, that just because all those trim pots are there....doesn't mean they need adjusting. Ever since, I've left everything to do with trim pots alone....until something made me adjust them.
 
Never touched any of my pots! I did drive the motor at 120HZ to get some rpm out of it because my motor is only 1740RPM.
 
Chris Railey said:
when I put the sub in should I not use GFCI breakers at all or just on the circuit for the grinder?
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Again, talk to your licensed electrical contractor. I would likely install GFCI's in all circuits of my house. However, upon further research I found this statement in KBAC's manual, Section 3
" Custom software: all models can be factory programmed for applications which require special timing, PLCfunctions, and GFCI operation – contact our Sales Department." This seems to say that the controller requires some kind of software upgrade to connect it to a GFCI circuit.
So, I suggest calling KBAC and clarify whether you can run your unit on a GFCI circuit. If not, have a separate non-GFCI circuit for your grinder.
 

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Chris Railey said:
A few years ago the big ice storm tore the mast off of my house. When it was fixed a 200 amp service was added outside but the inside panel was not upgraded. The wall I am going to add the sub-panel to is on the opposite side of the wall my feed comes to the house. So the sub-panel will be “fed” correctly. I have always thought that too low voltage is burning it up. That is why I am running it off of my inverter generator until I get my sub panel. Once I get my sub panel done I think I will switch my grinder over to 220v. I run currently on 115 too. So when I put the sub in should I not use GFCI breakers at all or just on the circuit for the grinder?
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Just on the grinder circuit.
 
Chris Railey said:
A few years ago the big ice storm tore the mast off of my house. When it was fixed a 200 amp service was added outside but the inside panel was not upgraded. The wall I am going to add the sub-panel to is on the opposite side of the wall my feed comes to the house. So the sub-panel will be “fed” correctly. I have always thought that too low voltage is burning it up. That is why I am running it off of my inverter generator until I get my sub panel. Once I get my sub panel done I think I will switch my grinder over to 220v. I run currently on 115 too. So when I put the sub in should I not use GFCI breakers at all or just on the circuit for the grinder?
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So your running your 3 Phase grinder on 120V with a KBAC27 off a Generator?
 
Yes, an inverter generator. I called tech support with KB Electronics and they said that would be fine. Its temporary anyway, every time I get lined up to do my panel install something goes wrong and We have to push it back. Hopefully soon.
 
Chris Railey said:
Yes, an inverter generator. I called tech support with KB Electronics and they said that would be fine. Its temporary anyway, every time I get lined up to do my panel install something goes wrong and We have to push it back. Hopefully soon.
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Maybe someone else could chime in on this because I'm not sure. I didnt think you could run a 220VAC motor on 120V? Just because the KBAC27 is rated for 120V doesn't mean the motor will run on 120V? Unless I'm understanding the whole concept wrong? I have a KBAC27 and run my 2HP 3PH motor on the dryer outlet in my basement. Never had a problem?
 
You can run the 2 HP motor on regular 115v with the 27D. The 27D has a 115v option, all you have to do is change a jumper wire. The drive converts single phase 115V to three Phase 220v. I do not know how, but that is what it does.
 
Gliden07 said:
Maybe someone else could chime in on this because I'm not sure. I didnt think you could run a 220VAC motor on 120V? Just because the KBAC27 is rated for 120V doesn't mean the motor will run on 120V? Unless I'm understanding the whole concept wrong? I have a KBAC27 and run my 2HP 3PH motor on the dryer outlet in my basement. Never had a problem?
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The KBAC 27D will accept either single phase 110V or 220V input voltage. The output is the same three phase 230V, except for a 2 HP motor is de-rated to 1 1/2 HP.
 
Chris Railey said:
You can run the 2 HP motor on regular 115v with the 27D. The 27D has a 115v option, all you have to do is change a jumper wire. The drive converts single phase 115V to three Phase 220v. I do not know how, but that is what it does.
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Same way it converts single phase to 3 phase...magic.
 
nerd alert... (file under: you'll be sorry you asked)

How a VFD makes 3 phase variable frequency from a fixed frequency input:

The output of a VFD is created inside the VFD on the power board. Sounds like an obvious statement, but it's not The distinction is that the VFD is not modifying what comes into it. It is changing what comes into it and creating something entirely different and sending it out. The input AC comes in and gets turned into DC Voltage on the power board. Just Voltage. Not current. Just a big pile of DC voltage sitting there waiting to be used. Then the control board takes over. The control board is the brain which controls the Power Board, where all the real work is done. On the power board, there are IGBTs (Insulated-gate bipolar transistor) which is a fancy way to say a remote-controlled On/Off switch. There are two of them connected head to tail so that when #1 fires, you get a big positive square wave as it turns on and off again. Then it's reversed mate fires, giving you an equal but opposite negative square wave. As this repeats, you have Alternating Current in the form of a square wave. How fast these IGBTs fire is how the VFD creates the output frequency. How tall the square wave is determines the voltage and the peak to peak distance between the waves is the Hertz. These VFDs are referred to as "Volts per Hertz" because they do vary the voltage with the frequency. It's a less expensive design with looser control tolerances, but it's an ideal way to run fans, pumps, and grinders- basically anything where you don't want herky-jerky motion and don't need to start and stop on a dime.

Getting three phase from single phase:

Imagine that your three phase VFD is what I described above. It just has three channels. Phase A comes in, gets turned into DC Voltage sitting on the power bus A, then the control board tells the output IGBTs how fast to chop it up, and you get a Variable Frequency output. Ditto on Phase B, and Phase C.

Well, the cool thing is once it's DC, you can do whatever you want with it. Heck, you have all this DC voltage sitting there on the DC Power Bus. The VFD can route that wherever it wants to. So it takes all the input AC and turns it into the combined DC Power Bus. Voila. That's how it turns single phase into three phase: it has a big DC Bus that feeds all three output channels. But this isn't free. You can't put out more than you take in, so the output is derated a bit (the average amount of total output can't be more than the average amount of total input).

The KBAC's aren't the only drives that do this. It's a pretty common feature on industrial VFDs. However, what's cool about the KBAC is that it will run off 110VAC and give you 230VAC out. But that's why it's limited to 2HP. You run out of 3 phase output pretty quick when you're trying to feed it with 110V single phase. It's really putting out about 1-1/2 HP when you do this and it's only possible because it's being used on a belt grinder which doesn't work very hard at all (compared to what VFDs do in industry).
 
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