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View Full Version : Spike Protection of CNC - Needed or Not?



Paul Alciatore
11-16-2007, 10:13 AM
Another thread had mention of burned out electronics on a CNC machine and that has me wondering. I work with a lot of electronics and know that the more sensitive equipment does need some protection from spikes and other trash on the power lines. This can depend a lot on local conditions as power quality varies a lot depending on location and the local power company. Don't get me started on that one.

I am sure it is a good idea to use a good UPS on a computer in a CNC setup, but what about the rest of the electronics and electrical circuitry? Any experience factors here? What is generally done and how often are there problems?

MTNGUN
11-16-2007, 10:36 AM
I've had far more problem with the PCs than with the drivers and power supply.

I live on top of a mountain and lose electrical equipment at least once a year due to power bumps and/or lightning.

Lost one original gecko 201 due to an errant metal chip.

Lost another original gecko 201 for unknown reasons. It didn't actually die, just ran rough.

As they fail, I am upgrading to the super-gecko (can't recall the model #) which is supposed to be tougher.

No power supply failures yet.

Realistically, the old PCs used for CNC are cheap and not worth protecting, as long as you have a spare handy and software backed up. I try to keep one or more spare PCs on hand all the time, but my software backup leaves something to be desired.

A power bump zapped the controls on my electric heat treatment furnace recently. I was able to retrofit a generic controller.

So far my VFD has survived unscathed, knock on wood.

Other equipment zapped: a satellite transceiver, an electric blanket,an external hard drive, numerous gfci's (but the devices plugged into the gfci's were undamaged).

I'm thinking about a homemade 220V UPS for my CNC lathe, not just for the electronics but the whole shebang. As it is, every time there is a power blip, the lathe crashes, it takes a while to recover, and sometimes the workpiece must be scrapped.

Weston Bye
11-16-2007, 11:15 AM
Spike protection goes both ways. The stepper/servo motor drives can be the source of spikes as well as the victims. Suppression between system elements is sometimes necessary. Locally generated spikes and surges can be the source of many unexplained failures.

Evan
11-16-2007, 12:01 PM
After theft the largest cause of loss of electronic equipment of all types is power problems. It exceeds fire, flood, and other natural disasters combined. No part is immune including purely electromechanical parts. I have seen breakers blown right out of the panel by a lightning strike nearby. With a good UPS you will not only have a degree of protection they will usually provide some sort of damage insurance. Depending on your system and the money invested it is possible to buy a transient suppressor that installs in the main panel which will protect the entire wiring system. If you live in an area with a lot of lightning that is a good idea. I have five separate UPS systems for my equipment that also have constant voltage transformers, a feature not usually found in most UPS units. On my satellite gear I use an expensive quick response time (10 ns) active tracking filter that has a crowbar circuit. In an out of spec condition over a certain threshold it clamps the incoming power to a dead short with a big thyristor and blows it's own fuses on neutral and hot.

I've never lost any gear to lightning yet. If it hits the drop to the house there is nothing that will protect your equipment and that's where the insurance policy comes into play. Closest hit I have had was to a tree a couple of hundred feet away. That's plenty enough to induce damaging transients in the power system even if it doesn't hit it. One of my neighbours had his satellite dish hit twice in a few years, frying his receiver both times. Another person that lived about half a mile away from our old house forgot to unplug the stove and fridge during a T storm, strictly electromechanical units. Lightning hit their power feed and fried both appliances.

ckelloug
11-16-2007, 12:08 PM
Take a look at www.brickwall.com They make some really tough surge protectors that use inductors and SCR's to clamp spikes that would explode a simple varistor based device. Not exactly cheap. Also, due to the configuration, they don't tend to pass high frequency line noise.

I've got one on my stereo.

--Cameron

Evan
11-16-2007, 12:46 PM
A simple isolation transformer will go a long way toward protecting equipment. The bigger the transformer the better it is as a low pass filter.

This one is good for about one horsepower.

http://vts.bc.ca/pics3/isoxfmr.jpg

It's important that if an isolation transformer is used that the isolation not be crossed by other connected equipment. Everything should be powered from the isolation xformer.