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No, the wire size would not cause this long of a startup time. A loose wirenut could, but I have a feeling you lost a phase somewhere.
3 Phase Breaker Tripping
- Thread starter phmade
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I looked at your picture. You have an Allen Bradley contactor (A26-30-10) and overload (TA25DU25). This is NOT your main problem, but the overload setting is a little low. Right now it is just slightly over 20 amps, but your motor is rated at 21 amps. Because it is a dust collector, it will be running close to full rated load.
After you diagnose the long, 10-second, startup, if the thermal overload trips under normal use, you could dial it up slightly. If it doesn't trip, then leave it where it is.
By the way, the other 2 dials appear to be set correctly, and they just control whether the thermal overload uses manual versus automatic reset.
P.S. When you are checking wirenut connections described previously, don't forget to inspect all of the terminal lugs on both the contactor and overload blocks.
After you diagnose the long, 10-second, startup, if the thermal overload trips under normal use, you could dial it up slightly. If it doesn't trip, then leave it where it is.
By the way, the other 2 dials appear to be set correctly, and they just control whether the thermal overload uses manual versus automatic reset.
P.S. When you are checking wirenut connections described previously, don't forget to inspect all of the terminal lugs on both the contactor and overload blocks.
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This is really a huge stretch and not likely to be true, but it is worth asking simply because I have seen people do this.
Some people mistakenly think that a wye configured motor means that it is supposed to be connected to power in a wye configuration too. This is not correct. Motors should always be connected as Delta (just 3 wires) to the incoming power. They can get away with it if they have 3-phase wye (120/208) power, but you do not. So make sure the previous owner did not connect either the neutral or ground to any of the wires inside the motor. The ground should be going to the metal frame of the motor, but not to any of the motor leads.
Your phase converter is the equivalent of an open-delta, and the neutral point is not a center point. (See the image I posted earlier). If the neutral or ground are connected to the center of the motor's wye configuration, it will pull the generated C-phase down to a low value.
Some people mistakenly think that a wye configured motor means that it is supposed to be connected to power in a wye configuration too. This is not correct. Motors should always be connected as Delta (just 3 wires) to the incoming power. They can get away with it if they have 3-phase wye (120/208) power, but you do not. So make sure the previous owner did not connect either the neutral or ground to any of the wires inside the motor. The ground should be going to the metal frame of the motor, but not to any of the motor leads.
Your phase converter is the equivalent of an open-delta, and the neutral point is not a center point. (See the image I posted earlier). If the neutral or ground are connected to the center of the motor's wye configuration, it will pull the generated C-phase down to a low value.
Michael Kellough
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Rick Christopherson said:
Thanks for that explanation Rick. I've puzzled over that more than once.
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Michael Kellough said:
You're not alone, Michael. A lot of people assume that motors don't conform to Ohm's Law because current and voltage appear to be inversely proportional during an under-voltage condition. They don't realize that resistance is not a constant in a motor, and it is what is changing that makes it appear that current and voltage are inversely proportional.
Motors still follow Ohm's Law, but resistance is a mathematical function of frequency.
phmade
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ok - partial success. I connected another 3 phase machine (edgebander) and it runs perfectly at the same time as the tablesaw. So I focused my attention on the dust collector wiring.
All wire nuts and connections are secure and correct at the motor. After inspecting the overload, I noticed that the reset button was "sticky" and inconsistent. I decided to bypass the thermal overload as a quick test. The dust collector starts within 5 seconds and the 3 phase breaker does not trip! I'm going to pick up a new thermal overload on Monday morning and confirm that's the problem.
Rick - I know you said that's not the main problem. Please let me know if you think there is something else incorrect here. I really just cannot figure out what else could be wrong. Especially since (2) other machines are running perfectly...
Thanks again to everyone. I'll post another update on Monday.
All wire nuts and connections are secure and correct at the motor. After inspecting the overload, I noticed that the reset button was "sticky" and inconsistent. I decided to bypass the thermal overload as a quick test. The dust collector starts within 5 seconds and the 3 phase breaker does not trip! I'm going to pick up a new thermal overload on Monday morning and confirm that's the problem.
Rick - I know you said that's not the main problem. Please let me know if you think there is something else incorrect here. I really just cannot figure out what else could be wrong. Especially since (2) other machines are running perfectly...
Thanks again to everyone. I'll post another update on Monday.
phmade
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Rick - I will review the motor wiring tomorrow to confirm. I don't think the ground or neutral are connected to any motor leads but I will double check. Thanks so much for your assistance. I really like a thorough explanation and you've given me one!
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Not enough is known here. Previously you said you had a 10 second startup and now it is 5 seconds. Is this a change, or were you just not specific on the previous time?
If it is a "change", then what changed in your system to account for it? You implied that removing the overload may have caused this change. However, this thermal overload is not a circuit breaker. It does not open any circuits feeding the motor. What this overload does is tells the contactor (a motor relay) that the contactor should open. In even simpler terms, the overload block just senses the current flowing through the wires, and if the current gets too high, then the overload tells the contactor to turn off the circuit. However, the wires passing through the overload block do not get disconnected. It simply acts as a signalling device.
So if removing the contact block is the only thing you changed to go from a 10 second startup to a 5 second startup, then you probably just had a poor connection somewhere between the contactor output and the motor input. If that's the case, you should be able to reinstall the overload block and still see the 5 second startup time, because what you corrected by removing it was a poor connection.
Now on the other hand, if you were mistaken about the 10 to 5 second decrease, then the setpoint on the overload does come into play and was more significant than I suggested in my previous posting. The setpoint of the overload should be increased. Start by setting it to maximum and see if the motor runs like it did with the overload removed. If it does, then dial it down to determine where it results in a trip. Normally you could reliably set this to the motor amperage rating of 21 amps, but because you are powering the motor from a phase converter, you may have one phase with a higher than typical amperage. This overload will sense that single phase and trip prematurely.
If it is a "change", then what changed in your system to account for it? You implied that removing the overload may have caused this change. However, this thermal overload is not a circuit breaker. It does not open any circuits feeding the motor. What this overload does is tells the contactor (a motor relay) that the contactor should open. In even simpler terms, the overload block just senses the current flowing through the wires, and if the current gets too high, then the overload tells the contactor to turn off the circuit. However, the wires passing through the overload block do not get disconnected. It simply acts as a signalling device.
So if removing the contact block is the only thing you changed to go from a 10 second startup to a 5 second startup, then you probably just had a poor connection somewhere between the contactor output and the motor input. If that's the case, you should be able to reinstall the overload block and still see the 5 second startup time, because what you corrected by removing it was a poor connection.
Now on the other hand, if you were mistaken about the 10 to 5 second decrease, then the setpoint on the overload does come into play and was more significant than I suggested in my previous posting. The setpoint of the overload should be increased. Start by setting it to maximum and see if the motor runs like it did with the overload removed. If it does, then dial it down to determine where it results in a trip. Normally you could reliably set this to the motor amperage rating of 21 amps, but because you are powering the motor from a phase converter, you may have one phase with a higher than typical amperage. This overload will sense that single phase and trip prematurely.
phmade
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Ok - here's an update:
Firstly - Rick, you're correct. The problem was not solved by removing the thermal overload. When I started the dust collector today, it tripped the 30A breaker in my 3 phase panel. So, I reviewed all of the wiring in the motor junction box. Everything was secure and consistent with the diagram on the nameplate. I did not actually check the wiring inside the motor - should I? In the junction box, there are 9 leads coming out. Three (T4,T5,T6) of the leads are are wired together and the remaining 6 leads are wired in 3 pairs. These pairs are consistent with the nameplate label on the side of the motor.
Regarding the startup time, I never accurately measured the startup time until today; therefore, I believe that it did not change; it was only my hopeful imagination. Today, I measured the startup time at 9 seconds before the breaker trips. I believe that the motor is still not up to full RPM at 9 seconds.
I also checked the current draw near the breaker and it is over 100amps for that entire startup period. On one startup attempt, the breaker did not trip and the current draw was between 12-13amps.
So now I feel that I'm back to square one. I'm trying to be methodical now to diagnose the problem. Could it be with the phase converter? Would the other 3 phase machines run correctly if that were so? My plan is to contact the phase converter company in the morning for recommendations. They are local and have been very helpful in the past.
I am not a professional electrician but I have done a fair amount of wiring including several homes and all other machines in my shop. I had an electrician here today (family friend) and he is equally as perplexed as I am. He has never worked with a phase converter though... My confidence is running pretty low at this point.
Firstly - Rick, you're correct. The problem was not solved by removing the thermal overload. When I started the dust collector today, it tripped the 30A breaker in my 3 phase panel. So, I reviewed all of the wiring in the motor junction box. Everything was secure and consistent with the diagram on the nameplate. I did not actually check the wiring inside the motor - should I? In the junction box, there are 9 leads coming out. Three (T4,T5,T6) of the leads are are wired together and the remaining 6 leads are wired in 3 pairs. These pairs are consistent with the nameplate label on the side of the motor.
Regarding the startup time, I never accurately measured the startup time until today; therefore, I believe that it did not change; it was only my hopeful imagination. Today, I measured the startup time at 9 seconds before the breaker trips. I believe that the motor is still not up to full RPM at 9 seconds.
I also checked the current draw near the breaker and it is over 100amps for that entire startup period. On one startup attempt, the breaker did not trip and the current draw was between 12-13amps.
So now I feel that I'm back to square one. I'm trying to be methodical now to diagnose the problem. Could it be with the phase converter? Would the other 3 phase machines run correctly if that were so? My plan is to contact the phase converter company in the morning for recommendations. They are local and have been very helpful in the past.
I am not a professional electrician but I have done a fair amount of wiring including several homes and all other machines in my shop. I had an electrician here today (family friend) and he is equally as perplexed as I am. He has never worked with a phase converter though... My confidence is running pretty low at this point.
phmade
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Hi John,
My sliding tablesaw (Altendorf) is also 7.5HP with a 1HP scoring motor. It starts and runs fine. It also draws over 100amps on startup but it is running at full RPM in less than 1 second and then the current draw drops below 10A.
The phase converter is rated to start a 10HP motor and is rated to run 25HP combined.
Phil
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phmade said:
The main thing you need to focus on is why do you have such a long startup time. This is what is causing the secondary symptom of the tripping 30 amp breaker. Don't focus on the breaker, because it is doing exactly what it is supposed to do.
[list type=decimal]
[*]Check the motor for free rotation. Make sure the impeller or motor shaft spins freely and continues to freewheel after you stop turning it by hand. If it doesn't freewheel easily, then look for obstructions such as dust. If no obstructions, then it is likely that the motor bearings are shot.
[*]Disconnect the motor, energize the motor contactor (turn it on), and then check the voltages A-B, A-C, & B-C at the motor. These voltages should be the exact same as they are back at the output of your phase converter.
[*]Reconnect the motor and repeat the above voltage measurements. It is expected that they will be slightly lower than the voltages at the phase converter, but it shouldn't be a huge drop.
You will only have 9 seconds to take each measurement, so it is expected that you may need to do this 3 separate times for the 3 readings. Let the motor cool down a little bit between each attempt. For the 9 seconds, the windings will have high amperage and they will get hot pretty quickly.
[*]If the C-phase voltages recorded in step 3 dropped really low, then start your tablesaw with no sawblade (no load) and repeat step 3. Your tablesaw will actually act as a secondary idler motor of the phase converter.
[/list]
phmade said:
This would suggest that on at least one occasion the motor did reach full speed. Given the amperage of about 50% of full load, then it also suggests the motor was successfully running at no-load (inlets blocked and bearings not seized).
One thing we haven't discussed much is your phase converter. You said it was a rotary converter and I assumed that to be correct. So let's confirm this. Does it have an idler motor that runs when the converter is started? If it doesn't have a big motor, then it is not a rotary converter. A static converter is not recommended for a dust collector motor.
phmade
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The motor and impeller spin VERY freely. In fact, it takes about 5 minutes for it to stop spinning after a startup attempt.
I will complete the other 3 steps in the morning.
I think it would be odd if the motor bearings are shot as it worked fine 2 weeks ago when I purchased it from another shop. I was careful during transport; however, I did lay the motor on a 45 degree angle when transporting. I wonder if this could have caused oil/grease to drain from around the bearings? I'm not familiar with the internals of these motors...
The motor did reach full speed on the first attempt and the breaker did not trip. I ran it for about 2 minutes before turning it off. Most of the inlets are blocked, but I have (2) 4" inlets still open. I think that's pretty minor on a dust collector this size.
Yes, this is a rotary phase converter with a large idler motor. I purchased it from ARCO electric. Here is the link to the exact product (It's a model B). http://www.arco-electric.com/Product.aspx?ProductID=1
You mentioned the motor getting hot. Are you talking about the DC motor or the phase converter idler motor? I noticed that the Idler motor had gotten quite warm (I could hold my hand on it but it was pretty hot) but the DC motor was still cool to the touch.
RJNeal
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[popcorn]
I'm watching this tread for I have a three hp,16" jointer I'm trying to run off a 7.5 hp rotary phase converter. It was running fine with a long start up. (5-7seconds). Then it started to trip it's breaker. Found a loose connection. Ran fine again then started to trip again.
I haven't looked at the wiring yet.
Thanks Rick for all the great info and trouble shooting. I now have info to look in to this problem.
Good luck phmade
Rick
I'm watching this tread for I have a three hp,16" jointer I'm trying to run off a 7.5 hp rotary phase converter. It was running fine with a long start up. (5-7seconds). Then it started to trip it's breaker. Found a loose connection. Ran fine again then started to trip again.
I haven't looked at the wiring yet.
Thanks Rick for all the great info and trouble shooting. I now have info to look in to this problem.
Good luck phmade
Rick
phmade
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More new developments to report:
I tested voltages at the motor during startup and... Once again, Rick is correct!
The C Phase Voltage dropped from 270V to 170V. I've been on the phone with the Phase Converter Manufacturer and they believe they need to add another bank of capacitors. Luckily, they are a local company about 30 minutes from me so I'm hoping to get this repaired/replaced today.
I have not tried running the tablesaw without the blade yet. Could that damage the tablesaw motor? This is a new tablesaw and I definitely don't want to damage that motor!
Thanks again for all of the assistance. I will post more as I have updates. Once again, the FOG is proving to be the best forum online - filled with knowledgeable, generous people!
I tested voltages at the motor during startup and... Once again, Rick is correct!
The C Phase Voltage dropped from 270V to 170V. I've been on the phone with the Phase Converter Manufacturer and they believe they need to add another bank of capacitors. Luckily, they are a local company about 30 minutes from me so I'm hoping to get this repaired/replaced today.
I have not tried running the tablesaw without the blade yet. Could that damage the tablesaw motor? This is a new tablesaw and I definitely don't want to damage that motor!
Thanks again for all of the assistance. I will post more as I have updates. Once again, the FOG is proving to be the best forum online - filled with knowledgeable, generous people!
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You've already been running the tablesaw for quite a while, I assume. So running it unloaded to take these measurements will not cause any new damage to the motor. I recommend that you complete the 4 steps listed above and present the results. Make sure you tell me everything, and don't withhold anything that you think is unimportant.
I do want to see if there is a difference between the tablesaw running and not running. As a matter of fact, lets add one more set of measurements.
Measure the voltages with only the tablesaw running. Then measure the voltages of the dust collector both with and without the tablesaw running.
I do want to see if there is a difference between the tablesaw running and not running. As a matter of fact, lets add one more set of measurements.
Measure the voltages with only the tablesaw running. Then measure the voltages of the dust collector both with and without the tablesaw running.
phmade
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My saw does have a computer controlled fence and blade height/angle.
I have NOT been running this saw. I am in the process of installing (3) machines: the dust collector, the tablesaw, and an edgebander. I recently purchased all 3 machines and they have never been run in my shop. The phase converter is also a new purchase to run these machines.
I spent most of the day on the phone with ARCO (phase converter manufacturer) and tech support for the other machines. ARCO seems to think that a start-up kit will be necessary to start the dust collector quickly. I'm not really sure what is included in a start up kit, but they are providing it as a solution. It should be ready for installation tomorrow. I have also been speaking with tech support for the tablesaw and edgebander to verify that I connect the high-leg from my phase converter in the correct location. I have taken more voltage readings than I ever cared to, but I think we're getting close to solutions. Hopefully I have good news to report tomorrow.
Rick, I think I'll try the start-up kit for the dust collector tomorrow if it arrives early enough. If it doesn't arrive, then I'll follow your steps with the tablesaw running. Thanks again.
-Phil
