fastline12
Aerospace
- Jan 27, 2011
- 306
Have a few odd question and figured I would roll them all into one.
1. I believe a running but unloaded 3P motor on a electric service has the effect of damping inrush seen by the power company when another motor starts up? IE, the already running motor helps start the next motor. Is there a way to calculate or quantify the potential energy held within a running induction motor?
2. Would it be accurate to say an isolation transformer behaves in a similar way to hold potential energy and would work to snub inrush currents seen on the primary side? Nevermind the obvious difference in current due to any step up/down in voltage. Just focusing on inrush that might be seen on the secondary, but not so much on the primary.
We have a limited electric service that cannot have nasty inrush spikes so as long as we keep our current draw as consistent as possible, our power company will be happy. In thinking about snubbing other motor starts, we considered just getting a rather large 3P motor to run as an idler to help snub inrush currents. What I would like to do is start the big motor on a small VFD and ramp it up VERY slow so as to not trip the VFD on over current. Once the motor is to speed though, I need to switch the motor right to grid power and shut down the VFD. just using the VFD as a soft start. I know they make soft starters but but sure how soft they really are and we would be starting a good size motor and would not be able to support the inrush requirement.
1. I believe a running but unloaded 3P motor on a electric service has the effect of damping inrush seen by the power company when another motor starts up? IE, the already running motor helps start the next motor. Is there a way to calculate or quantify the potential energy held within a running induction motor?
2. Would it be accurate to say an isolation transformer behaves in a similar way to hold potential energy and would work to snub inrush currents seen on the primary side? Nevermind the obvious difference in current due to any step up/down in voltage. Just focusing on inrush that might be seen on the secondary, but not so much on the primary.
We have a limited electric service that cannot have nasty inrush spikes so as long as we keep our current draw as consistent as possible, our power company will be happy. In thinking about snubbing other motor starts, we considered just getting a rather large 3P motor to run as an idler to help snub inrush currents. What I would like to do is start the big motor on a small VFD and ramp it up VERY slow so as to not trip the VFD on over current. Once the motor is to speed though, I need to switch the motor right to grid power and shut down the VFD. just using the VFD as a soft start. I know they make soft starters but but sure how soft they really are and we would be starting a good size motor and would not be able to support the inrush requirement.