I got a mill with a 5 horse 3 phase motor. My shop has 30 Amp 220 single phase. A vfd seems like the best way to power the mill, but I'm concerned that if anything else kicks in (air compressor) I'll trip my breaker. Then run back to the house. Obviously I need some emergency lighting so I can find my way out, and long term the plan is to dig in some bigger wire. For now my concern is the vfd, should I worry about it if the power goes off on the input side often?
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Is tipping the breaker bad for a vfd?
- Thread starter HMiller
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Do you already have issues with the breaker tripping? Keep in mind that 3-phase 220 motors use less amps than lower voltage motors. The easy fix is to simply turn off the other high draw items in your shop while using the mill, but VFD’s are fairly well protected from power loss, unless the problem occurs AFTER the VFD, ie a short in the motor
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I think frequent tripping, especially when the motor is heavily loaded, would not be good for the VFD. Severe voltage transients are produced and can damage solid state circuitry
-Mark
-Mark
My compressor trips the 20amp breaker it shares with a dehumidifier when it restarts under pressure (the pressure release doesn't seem to be working). But that is the only load I have, this mill is the first thing with any reason to worry.
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i would find other means of powering both units separately or repair the compressor
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Yes! Tripping a breaker could fry your VFD.
VFD powered motors are much less likely to trip a breaker though. The soft start feature GREATLY lowers the current needed to start a 3 phase motor. The huge inrush current when starting a motor is what usually trips breakers... like your compressor.
VFD powered motors are much less likely to trip a breaker though. The soft start feature GREATLY lowers the current needed to start a 3 phase motor. The huge inrush current when starting a motor is what usually trips breakers... like your compressor.
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IMHO, the last couple posts have confused the OPs original question. That is, if a VFD looses power; does it harm it? The answer is no harm.
I have VFDs with contactors on my CNC machines. An Estop drops the contactor. This is a VERY COMMON design. never seen or heard of an issue.
Now if you are in the middle of a cut, expect broken tooling. And very likely a mark on your part.
Now you really should get that compressor repaired. Your unloader valve is out. I have a compressor where I was unsuccessuful in repairing the old unloader so i used an air solenoid and timer to always unload at startup. In my case the VFD was the timer. Any delay on start would work.
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I have VFDs with contactors on my CNC machines. An Estop drops the contactor. This is a VERY COMMON design. never seen or heard of an issue.
Now if you are in the middle of a cut, expect broken tooling. And very likely a mark on your part.
Now you really should get that compressor repaired. Your unloader valve is out. I have a compressor where I was unsuccessuful in repairing the old unloader so i used an air solenoid and timer to always unload at startup. In my case the VFD was the timer. Any delay on start would work.
Understand unloader valves
There is two types of unloader valves. The ones most are familiar with, unloads the pressure from the head, to the tank when the motor shuts off, making it easy to start up the next time. The other style, many big compressors have, unloads the head, when the pressure is reached, (Like what is...
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Last edited:
Stupid simple...
Turn off the compressor.
You can get more complicated by adding mag starter to compressor as this is better control.
Then on control line for starter interlock it with main switch for mill do both cannot be on at same time.
Easy to do.
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Turn off the compressor.
You can get more complicated by adding mag starter to compressor as this is better control.
Then on control line for starter interlock it with main switch for mill do both cannot be on at same time.
Easy to do.
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In theory, Karl is correct. BUT
In the real world, with cheaply made VFDs that have little in the way of snubbing and mov protection (metal oxide varistor)
Who knows what COULD happen. I have seen stuff blow up that shouldn't. I would rather be cautious.
-Mark
In the real world, with cheaply made VFDs that have little in the way of snubbing and mov protection (metal oxide varistor)
Who knows what COULD happen. I have seen stuff blow up that shouldn't. I would rather be cautious.
-Mark
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- Nov 23, 2017
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- 1,191
I hit the breaker to shut off my VFDs all the time and never seen anything negative happen..... I dont know where this crazy idea comes from that unplugging a VFD can damage it, everyone seems to think VFDs are made of glass.... I have a friend who is scared to buy one because he has this idea in his head..... I think it was AvE's fault with that video he made after he wired it wrong.....