The bypass contactor depending on the phase could be used to reverse the rotation of the motor depending on the controller in charge of the isolation contactor on the VFD output.
Back in the '90s, a friend bought a large 3-phase rotary converter for around $350 (it was one the guy had built, and the customer never came back for it). Not sure what it was rated, but he ran a 10hp 3-phase motor on it all day for years. I guess he still has it.
We talked to a guy about building another one, and he couldn't believe my friend had got one that cheap.
We talked to a guy about building another one, and he couldn't believe my friend had got one that cheap.
Winner winner! Now explain that to the effing moron that remodeled this house back in the 80's.
Changing the incoming wires to the drive will change both the drive contactor and the bypass contactor. Changing just the leaving on the drive contactor will still have the motor running the wrong way on the bypass or vise-versa. (Probably should have went more in-depth with the question)
You lose efficiency. A 5 hp motor will not produce 5 hp through an inverter or rotary converter. but some equipment designed for 3 phase needs to run on it for control reasons. A person could do a complete controls, motor upgrade but it would likely cost more than buying an inverter.
Yes, there are several possibilities. My example would be for the VFD to drive a conveyor at a controlled speed to meter the material on the conveyor, while the controller in charge of the entire system may have a safety built in to prevent a jam or stall by opening the isolating contactor and closing the bypass contactor with phases reversed to provide an automatic reversal of the conveyor belt. The controller in charge would have a timer that would only back up the conveyor belt for a pre-determined length of time then open both the isolation contactor and the main contactor to shut everything down, waiting on an operator reset.
Did you ever work with any of the PLC controls (or like controls) that they use to set something like this up?
Would be cheaper to replace the motor.
It would be great if they'd show up and do that lol... I have to run all new 250amp service from pole to house, from house to shop. Been calling for two years, nobody local has the interest to do it.
By controlling generator speed. A 2 pole generator requires 3600 rpm to generate 60 hz. A 4 pole generator requires half that speed.
When your bringing a power plant generator online, the phases are matched through the control system and a synchroscope that tells the generator where the grid phase is. When they match, there are two options. The operator can manually sync the generator by throwing a switch at the right time that is critical, or allow the later model electronic control systems to do it electronically.
When I say critical, it's a breathtaking moment when syncing a 550 megawatt steam driven generator to the grid. If your 1/10 of a cycle off, some bad stuff is fixing to happen. Huge 200' long generators have screamed to a halt and actually spun backwards. Never saw that, but had industry reports with details.
