Does the spindle or VFD shut down on overheating?

[gerald_d]

I don't have a SB-supplied spindle system and I wonder at times why my own experience with another spindle seems so different from what is talked about at this Forum.....

My Fimec spindle comes standard with a thermistor buried deep in its electrical coils to sense when things get too hot down there. Apparently, the Colombos also have this thermistor, and it is very common on more expensive motors.

But, this thermistor is only a sensor. It needs to be wired to a special "thermistor relay" before it it can actually do something like switching on a light, blowing a hooter, or shutting down the power. If you don't have a thermistor relay, you might have a false sense of security that this thermistor is going to save you from burning out the spindle.

Around here, these thermistor relays are not cheap, $100 and up. What do you guys have connected to your thermistors?

By the same token, the Delta VFD's can also output a signal if things are getting too hot in there - do you guys have a light/hooter/shutdown connected to this?

[elcruisr]

The VFD (at least mine) has a shutoff if the thermistor sensor overheats. The problem is your bearings can overheat and the thermistor never shuts it down. Another reason to use a temp mpnitor.

Eric

[gerald_d]

Eric, a thermistor in the spindle will have two wires coming out of it, but the Delta VFD has no facility for receiving these two wires. Am I missing something somewhere?

From this thread (http://www.talkshopbot.com/forum/show.cgi?tpc=312&post=29011#POST29011), I also got the impression that the thermistor is connected to the VFD, but it must be a different VFD to the Delta VFD-B that I have?
http://www.delta.com.tw/product/em/ac_motor/ac_motor_manual.asp for the recently revised manual.

[gerald_d]

After re-reading the VFD manual a couple of times, I am not even sure if the VFD will turn off immediately when overheating. It has a sensor which can drive an output relay, and that relay can be used to interrupt the "Run" signal, but the ShopBot "Run" signal does not go via that relay.

Has anybody ever seen an auto shutdown caused by heat? In either the spindle or VFD? Maybe I am just too heat conscious out here....

(We have set 03-00 to 08 (factory default) to trigger the onboard relay when there is an abnormality, and terminals RB & RC are in our "E-Stop" circuit. From SB's wiring instructions, there is nothing connected there?)

[elcruisr]

Well, the techs from Colombo gave me a bad schematic one time on my first spindle and shorted out the thermistor. I had to jump out the sensor circuit on my VFD or it would sense a thermistor problem and shut down the spindle. On mine the thermistor wires come back to the VFD box. It can also be turned off by a programming code. You can trash the spindle from overheated bearings but the thermistor won't catch that in time according to Colombo. That's why I keep an eye on bearing temps with an IR thermometer. I'm told that we are allowed 140F when sitting idle and 160F while cutting.

Eric

[richards]

Gerald,
Up here in the tops of the mountains, we don't get daytime temperatures much over 105-F inside the shop on the hottest Summer days, so I still have a little margin. A few days last Summer, I had to pause a little between each sheet of material to keep the IR temperature reading below 140-degrees. What I did find out, however, was that reading the bearings area was 10-15 degrees hotter than reading the motor area. Depending on just where the thermistor is located, you might get 'safe' readings, when, in fact, the bearings are at maximum temperature.

[gerald_d]

I think those techs might have confused the newer thermistor protection with the older thermal switch (Klixon). The "Klixon" could have been connected directly to a VFD, but a thermistor cannot. The SB'ers practice of measuring the outer bearing casing temp is the only thermal protection - the internal detectors are not connected.

My Fimec spindle came with strict instructions to connect the thermistor to a Euro standard relay if I wanted the warranty to apply. I suspect that the Italian office of Colombo would also want that - otherwise they won't install a thermistor in the first place. That thermistor might actually be right next to the bearing - they would have put it in the most important place to save them a warranty claim.

[gerald_d]

Mike, what is your altitude? Did you see in the Delta manual that your max operating altitude is supposed to be 1000 meters? (The economic heartland of this country is above that altitude)

[richards]

Gerald, I may have to dig a hole in the back yard for the Alpha. As near as I can tell, the altitude at the table, with the nose of the spindle just touching the spoil board is 1,295.704798 meters. However, the Civil Engineer that I consulted, doesn't think that I've adjusted the figures 3.847163mm for the early May frost heaves.

[gerald_d]

Those Greeks and their alphabet - it is not the Alpha that must be lowered, but the Delta.

The reason for the altitude limit is because the thinner air has less capacity to cool. 1000m is an unneccessarily low thumbsuck by the guy writing the specs - I doubt that they actually did lab tests to arrive at that figure.

[watswood]

Gerald, I was told by the Columbo techs that the 'thermo switch' trips at 195 deg. F. My wiring diagram that came with the spindle indicates that this device (the 'termoprotettore')is rated for 230v/3amps. Columbo suggests connecting this device to terminals M14 and DCM and programming parameter 02-02 to 02 and 04-07 to 20. This would shut down the spindle if the switch would ever trip. My guess is that this switch is designed to prevent a catastrophy such as a short, and not designed to protect against running a spindle hard on a hot day. As Eric mentioned, it won't save the bearings. Maybe they feel the bearings are replaceable and the windings are not. The question is, with a short, what would happen first, the thermo-switch signaling the vfd to shut down or frying the vfd's output transistors?

Connecting rb and rc to the estop is a good idea. I'm not sure shopbot does it.

[richards]

Would something as simple as a box fan blowing on the outside of the spindle dissapate enough heat to make a difference? Mounting an extra fan to cool the outside of the spindle might help the fan that blows through the spindle be more efficient.

(I had to stop digging a few hours ago. You were right, the deeper I dug, the thicker the air became. At about ten feet down we started hitting relics of some sort. I'm not sure what they were, but . . . )

[mikejohn]

I think you should be raising the Alpha, not lowering it.
The closer you go to sea level, the greater the outside air temperature.
Stick it up to 3,000m, its very cold up there!
From what Delta say, does this mean it would overheat in the vacuum of outer space?

...............Mike

[gerald_d]

Eugene, thanks a lot for that post! A 230V/3Amp "thermoswitch" is a completely different animal to a "thermistor". If the Colombos have the switches (some call them Klixons), then they can be connected to shut down the VFD. Seems like my confusion is being caused by the nomenclature.

Yes Spaceman Mike, something that relies on air to keep it cool, needs.........air.


Digger Mike, did any of those relics resemble the old family portraits? From pics of Colombos, it appears that the fan cowl does blow some air down the outside of the casing.

[gerald_d]

The Wikipedia on thermistor:
http://en.wikipedia.org/wiki/Thermistor

Thermistors are much smaller, cheaper, more reliable and more predictable than a "thermoswitch". Often 2 or three thermistors are placed in equipment, all connected in series. The thermistors in a motor could have different temperature values, depending on the location that they are monitoring. Because they are such low current devices, their wiring is thin and they are not obtrusive to the rest of the machine.

But, a sensing system must be placed outside the machine. And this is where the standardised "thermistor relays" come in. It does seem that the use of thermistors is still a fairly young technology and hence the high prices of the relays.

It would be a simple matter to strap/glue a thermistor to the bearing housing and rig a relay to it.