Voltage Problem Solution
Voltage Problem Solution
(OP)
Hello Engineers! Hope you guys are doing well but I am not. Let me explain.
Last couple of month we are having imbalance voltage problem. We got the main power connection from our national grid. Our line voltage is 33KV. We are using two step down transformer. First one is 33/11KV second one is 11/0.415KV. Both transformer has individual auto tap changing panel. It automatically adjust the rated voltage 380-400V according to our machinery. But sometime our main line voltage drop at 26KV. Yes, transformer can adjust the output voltage by changing its tap position. It takes 30 seconds for each tap changing. But if there is a sudden voltage drop or up like 30 to 25 or 27 to 31 in a second then all machines inside the factory go offline and sometime electronic components like PLC, Inverter goes damage by this sudden millisecond voltage fluctuation. We tried a lot for solving this problem but failed. So guys, can you tell me how we can save our machines from this sudden voltage fluctuation?
Thanks in advance!
Last couple of month we are having imbalance voltage problem. We got the main power connection from our national grid. Our line voltage is 33KV. We are using two step down transformer. First one is 33/11KV second one is 11/0.415KV. Both transformer has individual auto tap changing panel. It automatically adjust the rated voltage 380-400V according to our machinery. But sometime our main line voltage drop at 26KV. Yes, transformer can adjust the output voltage by changing its tap position. It takes 30 seconds for each tap changing. But if there is a sudden voltage drop or up like 30 to 25 or 27 to 31 in a second then all machines inside the factory go offline and sometime electronic components like PLC, Inverter goes damage by this sudden millisecond voltage fluctuation. We tried a lot for solving this problem but failed. So guys, can you tell me how we can save our machines from this sudden voltage fluctuation?
Thanks in advance!






RE: Voltage Problem Solution
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Voltage Problem Solution
RE: Voltage Problem Solution
https://www.anelectricalengineer.com
RE: Voltage Problem Solution
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Voltage Problem Solution
If it's motor loads, then what Bill posted will work. Use a UPS system on the control circuits. Keep the controls alive and the motors connected to the grid and they will ride-through a voltage dip that is under 1 second.
Any system to regulate the line voltage to ride through transients will be expensive.
RE: Voltage Problem Solution
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Voltage Problem Solution
https://www.anelectricalengineer.com
RE: Voltage Problem Solution
https://www.anelectricalengineer.com
RE: Voltage Problem Solution
This unit from Hammond, if set to receive 30 kV will handle 10% over voltage. That lets you handle 33 kV at the top end.
This unit will handle minus 25%. From 30 kV that is a low of 22.5 kV, or
Set for 33 kV supply this will go down to 24.75 kV.
That looks as if it will handle your range of voltage fluctuations.
I am not recommending this line. I am showing this as an example of what is available.
There are other manufacturers and similar units are available for 50 Hz.
Link
Link
There are three ways to go;
One, break out each control circuit and power each control circuit with a single small Constant Voltage Transformer.
Two, break out each control circuit and power all the control circuits with a single, larger, Constant Voltage Transformer.
Three, feed each machine or each VFD with three Constant Voltage Transformers connected in delta.
Google is your friend.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Voltage Problem Solution
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Voltage Problem Solution
You describe them as running at a low speed. Typically, with a VFD you don't need rated voltage to run the motor at a lower speed. For example, the motor could be run continually just fine up to 75% speed with 25kV input.
However, the VFD might have a fixed low voltage trip built-in that you can't bypass or adjust and that will trip when the voltage drops to 25kV. So, you have to check into it to see if the VFD can keep operating with such a line voltage dip.
RE: Voltage Problem Solution
-Some LTC controllers have an inverse time curve available to speed up LTC steps for large voltage variations. This might be able to reduce your time from the voltage reduction to the first step down to a couple of seconds. This can have detrimental impacts to the overall transmission network during a voltage collapse scenario, so talking with your transmission provider before implementing this is a good idea.
-Tap changers can be set to either operate continuously until the voltage returns within bandwidth, or they can be programmed for non-sequential operation where each tap change has a delay. Changing your mode of operation may allow the voltage to be returned to normal within 30 seconds total instead of 30 seconds per tap.
RE: Voltage Problem Solution
https://www.anelectricalengineer.com