We have 480 3 phase Y that runs a little low 475 VAC and we get power sags once every 2-3 months probably milliseconds. This causes a machine fault. Was looking into boost using 3 buck boost transformers that would take it to 501 VAC this is on a 480VAC 89 amp requirement automated pump control. Thoughts??
Using buck boost transformer to over come intermittent voltage sags 480 vac
- Thread starter Wildwoody
- Start date
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Welcome to the forum.
A transformer will boost the voltage 24/7 as well as the cost of energizing it.
What you need is voltage regulation, such as a UPS or other stabilizing unit.
A transformer will boost the voltage 24/7 as well as the cost of energizing it.
What you need is voltage regulation, such as a UPS or other stabilizing unit.
The cost for each machine would be around $3000.00 each time it happens it shut the whole process down while machining looking into a 3 phase UPS is very expensive. And again it could be in milliseconds not sure of the duration. Thanks for the suggestion.
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
How deep is the sag and what is the threshold for problems?
What is the voltage range that the machine is designed for?
As @LarryFine says, a boost transformer will do nothing for voltage regulation. It only shifts your starting point. If the sags are small and the machine can handle the extra baseline voltage, then a boost might help. But if the sags are deep then the boost won't help.
What is the voltage range that the machine is designed for?
As @LarryFine says, a boost transformer will do nothing for voltage regulation. It only shifts your starting point. If the sags are small and the machine can handle the extra baseline voltage, then a boost might help. But if the sags are deep then the boost won't help.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
One problem of using buck-boost transformer to solve voltage drops, due to loads, is the possibility if overvoltage as the load decreases.
You might want to look into constant voltage transformers.
You might want to look into constant voltage transformers.
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
Do you have any scope traces of these power sags? Solving a 5 mS problem is very different from solving a 1 second problem.
Are you assessing the power sag based on light flicker or something else?
Is the machine shutting down because the low voltage is actually causing a problem, or because some protective alarm is noticing the low voltage and tripping the machine off before the low voltage would directly cause a problem?
Are you assessing the power sag based on light flicker or something else?
Is the machine shutting down because the low voltage is actually causing a problem, or because some protective alarm is noticing the low voltage and tripping the machine off before the low voltage would directly cause a problem?
Constant voltage (ferro resonant) transformer, but only for the control power, control boards. Not for the entire machine.
Make sure line to line Voltage matching is good, less than 1% line to line imbalance. The motor may tolerate underVoltage well, if the line to line Voltages are all the same.
Find out exactly what is throwing the fault, control board, drive, protective relay. I would look at how much of the machine can ride through and what cannot or does not.
Make sure line to line Voltage matching is good, less than 1% line to line imbalance. The motor may tolerate underVoltage well, if the line to line Voltages are all the same.
Find out exactly what is throwing the fault, control board, drive, protective relay. I would look at how much of the machine can ride through and what cannot or does not.
Answering all the replies is easier when I get caught up. Very early into some of the questions duration, total drop, and usually we know we had a sag is when just these 5 machines fault out because of a low DC bus for the VFD controls. Everything else in the plant can handle the sag. Which is at least 50 plus 480 VAC powered. Also haven't reached out to the OEM if they have a solution for increasing the tolerance. Thanks again for the input.
Knightryder12
Senior Member
- Location
- Clearwater, FL - USA
- Occupation
- Sr. Electrical Designer/Project Manager
You need a voltage regulator style transformer. I have used ones from Controlled Power Company. I have used the Series 700A Power Processor. They say they can correct voltage variations from +13% to -40%.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
- Occupation
- Electrician
Sounds like boosting the voltage a little bit may help if it makes enough of a difference to keep you out of that low bus V fault threshold. I would probably want to have logger data to see how much voltage I would need and make sure that doesn't exceed the voltage when the voltage is at its highest .
Strathead
Senior Member
- Location
- Ocala, Florida, USA
- Occupation
- Electrician/Estimator/Project Manager/Superintendent
Did anyone ask what is causing the sags? Or more specifically, from the utility in, what is causing the voltage to be low at the piece of equipment? I can think of so many scenarios and possibly multiple solutions for each.