Band saw tripping overload

[guest]

My Kalamazoo Cold Saw was tripping the thermal overload, it was the spindle bearings. Couldn't hear it, but you could feel it and new bearings solved the problem.

 

[Guest]

In process of checking. One thing I did try something that was cut all equipment on at same time which was 2(5HP) 1(1hp) 1(1.5hp) 1(2hp). I checked my voltage output for RPC and it was pretty close to the same. And the saw didnt trip the overload. So i'm studying on how to balance the voltage (i think its my problem) its not common to run all at once.

The reason for large RPC is i paid $300 for it, replace the switch that kicks start up caps out, has been working pretty good.

When everything was running did you check the voltage at the saw? Is it possible all the equipment running creates a low voltage issue at the saw which drives up the amps and trips the overload? Sorry, from experience and what voltage ranges I have successfully run motors on I am not buying balancing as an issue.

 

[jaddy]

When everything was running did you check the voltage at the saw? Is it possible all the equipment running creates a low voltage issue at the saw which drives up the amps and trips the overload? Sorry, from experience and what voltage ranges I have successfully run motors on I am not buying balancing as an issue.

All the cap check good.
Things actually work better with everything running values with everything running was

L1-L3 257
L2-l3 243
L1-l2 240
Amp
l3. 5.5
L1 6.6
L2- 2.7

 

[ewlsey]

How did you check the caps? Do you have an ESR meter?

 

[jaddy]

How did you check the caps? Do you have an ESR meter?

I used a fluke 373 meter

 

[atomarc]

It sure seems to me that something is working that motor pretty hard..it's huffing and puffing.

Stuart

 

[jaddy]

It sure seems to me that something is working that motor pretty hard..it's huffing and puffing.

Stuart

I agree. Took the belt off and ran motor sounds rough. Bearing maybe also hear intermittent buzzing inside.

Anyone think a 3/4hp single phase motor would work just as good, got one laying around the right frame

 

[atomarc]

Isn't the saw already wired up for 3 phase?

Breaking a 3 phase motor apart for a exam and bearing replacement is a 1/2 hour job..provided there is no shaft or end-bell bearing seat damage. If your current motor is a 2hp I don't think a 3/4hp is going to do it.

Stuart

 

[SAF]

In process of checking. One thing I did try something, that was cut all equipment on at same time which was 2(5HP) 1(1hp) 1(1.5hp) 1(2hp).

I checked my voltage output for RPC and it was pretty close to the same. And the saw didnt trip the overload. So i'm studying on how to balance the voltage (i think its my problem) its not common to run all at once.

The reason for large RPC is i paid $300 for it, replace the switch that kicks start up caps out, has been working pretty good.

Looks like once it was a little more loaded, and the balance was better, everything was working well enough to stay running, even with the mechanical/electrical problem you discovered with the saw motor.

I would point out that that in your test, you connected 14.5HP of idling load. A 25HP RPC unit would normally be balanced to easily carry that load, fully loaded, and still be pretty close to balanced, and even more.

As others stated earlier, that overload was doing its thing. With a binding motor and better voltage balance, that overload is now, just fine carrying a slight overload, with a slight imbalance, same condition the motor is dealing with.

All the cap check good.
Things actually work better with everything running,
The values with everything running was:

Volts -----------Amps
L1-L3 257 ---L3. 5.5
L2-l3 243 ----L2- 2.7
L1-l2 240 ----L1 6.6

NEC code full load nameplate value for 2HP 230V 3Φ is 6.8A
So the test showed that the motor runs within its current limits, when the supply voltage is within the +/-10% design limits.

To balance your RPC, you should first consider your connected load size, future additional loads, and then how you will run them. The caps could be switched in and out, depending on the way you run the loads if that is really required.

Some manufactures of RPC's will recommend that for sensitive loads like CNC's, that you have an individual RPC selected for each CNC machine, to better stabilize and isolate the power supply for best performance. Maybe excessive in your case, but illustrative of the conditions that can arise with one large RPC, is used for everything.

I am running with a phase converter which is plenty large enough.

Probably a bit too much, for a 2HP saw with an IEC overload, and a binding motor.

Since you found cap oil in the enclosure, but all the caps checked good. I would suspect that the oil is from the old start caps that likely blew, when the start relay gave up the ghost, with the previous owner.

If you have it apart, show us what your working with. We like pictures...

SAF Ω

 

[Guest]

I agree. Took the belt off and ran motor sounds rough. Bearing maybe also hear intermittent buzzing inside.

Anyone think a 3/4hp single phase motor would work just as good, got one laying around the right frame

The motor control system in the saw is set-up for a 2HP motor, unless your 3/4HP motor has it's own overload protection (usually evidenced by a reset button on the outside case) that 3/4 HP could draw enough to catch fire before the machine trips any overloads. Bad idea!!!

 

[jaddy]

Looks like once it was a little more loaded, and the balance was better, everything was working well enough to stay running, even with the mechanical/electrical problem you discovered with the saw motor.

I would point out that that in your test, you connected 14.5HP of idling load. A 25HP RPC unit would normally be balanced to easily carry that load, fully loaded, and still be pretty close to balanced, and even more.

As others stated earlier, that overload was doing its thing. With a binding motor and better voltage balance, that overload is now, just fine carrying a slight overload, with a slight imbalance, same condition the motor is dealing with.



NEC code full load nameplate value for 2HP 230V 3Φ is 6.8A
So the test showed that the motor runs within its current limits, when the supply voltage is within the +/-10% design limits.

To balance your RPC, you should first consider your connected load size, future additional loads, and then how you will run them. The caps could be switched in and out, depending on the way you run the loads if that is really required.

Some manufactures of RPC's will recommend that for sensitive loads like CNC's, that you have an individual RPC selected for each CNC machine, to better stabilize and isolate the power supply for best performance. Maybe excessive in your case, but illustrative of the conditions that can arise with one large RPC, is used for everything.



Probably a bit too much, for a 2HP saw with an IEC overload, and a binding motor.

Since you found cap oil in the enclosure, but all the caps checked good. I would suspect that the oil is from the old start caps that likely blew, when the start relay gave up the ghost, with the previous owner.

If you have it apart, show us what your working with. We like pictures...

SAF Ω

 

[SAF]

25HP RPC Balancing

Comments from the pics.

Looks like you got a pretty big bank of run caps in there. 12 units of substantial size.

And only 2 large start caps.

The thing I like about the build construction is that they used an individual pair of wires for each run cap. Many folks use one pair for several caps, and jumper them together. This creates weak connection points at the capacitor faston spade terminals. Those caps can carry quite a bit of current each, when loaded, and the faston terminals are usually rated for 10-15 amps each.

The bad part, that you can't really see in the photos, is that the cap wires are all terminated to the motor leads, with split bolts, covered in tape. It's a solid connection method, but more of a pain to modify the connections, for a re-balance.

One thing to be aware of with balancing, is the balance of caps between running and starting.
During starting both run caps and start caps, contribute to the phase shift capacitance of the third generated leg. When you remove some run caps, that can leave the start caps, a little shy on a timely motor startup, stressing the start relay and caps.

Ideally with a new build you would want to size the run caps first. Rope or pony starting the unit, and adjusting the run caps till your happy with the voltage balance result. You want the unloaded output voltages to be about 3-5% higher than the line voltage. Then connect the start circuit and adjust the start caps, until you get a quick start. A second or two. Too much start cap can make the startup current excessively high, but very quick. To little start cap will make the startup longer, and heat up the start caps, which are only rated for intermittent use.

Any excess run capacitance disconnected, can be reused on the start side, if that becomes necessary, as long as the start relay contacts can handle the additional current.

To use as an additional reference, HERE is a link to a 30HP RPC that the member Bnelson shared with the forum years ago. He's using a few less run caps (9 * 60uF = 540uF) and more start caps (8 * 300uF = 2400uF).

Check your numbers and compare to his, for a ball ball park figure. His is 5HP bigger, but he is running all his machinery off the same unit, like you want to do. Yours may have been designed and setup for one large load. And HERE is the thread that the link came from, for further reading.

SAF Ω

 

[jaddy]

Comments from the pics.

Looks like you got a pretty big bank of run caps in there. 12 units of substantial size.

And only 2 large start caps.

The thing I like about the build construction is that they used an individual pair of wires for each run cap. Many folks use one pair for several caps, and jumper them together. This creates weak connection points at the capacitor faston spade terminals. Those caps can carry quite a bit of current each, when loaded, and the faston terminals are usually rated for 10-15 amps each.

The bad part, that you can't really see in the photos, is that the cap wires are all terminated to the motor leads, with split bolts, covered in tape. It's a solid connection method, but more of a pain to modify the connections, for a re-balance.

One thing to be aware of with balancing, is the balance of caps between running and starting.
During starting both run caps and start caps, contribute to the phase shift capacitance of the third generated leg. When you remove some run caps, that can leave the start caps, a little shy on a timely motor startup, stressing the start relay and caps.

Ideally with a new build you would want to size the run caps first. Rope or pony starting the unit, and adjusting the run caps till your happy with the voltage balance result. You want the unloaded output voltages to be about 3-5% higher than the line voltage. Then connect the start circuit and adjust the start caps, until you get a quick start. A second or two. Too much start cap can make the startup current excessively high, but very quick. To little start cap will make the startup longer, and heat up the start caps, which are only rated for intermittent use.

Any excess run capacitance disconnected, can be reused on the start side, if that becomes necessary, as long as the start relay contacts can handle the additional current.

To use as an additional reference, HERE is a link to a 30HP RPC that the member Bnelson shared with the forum years ago. He's using a few less run caps (9 * 60uF = 540uF) and more start caps (8 * 300uF = 2400uF).

Check your numbers and compare to his, for a ball ball park figure. His is 5HP bigger, but he is running all his machinery off the same unit, like you want to do. Yours may have been designed and setup for one large load. And HERE is the thread that the link came from, for further reading.

SAF Ω

That was the problem unbalanced. I unplugged 3 run caps and the saw run smooth as ever! and 5hp lathe ran well within range of voltage, Im a one man operation and seldom everything going at once.
with unplugged
l1-l3 264
l2-l3 246
l1-l2 240
still a gap but better Im afraid to unplug any more because of 246v, it starts slow so im gonna have to add some to start side.
Thanks everyone for there input.