PDA

View Full Version : Switching a 220V single Phase line



hammerfest
08-09-2010, 01:00 AM
Gents--I have 3HP motor on my newly acquired mill (Bridgeport Clone). I have a VFD to convert to three-phase for the motor. At present all work well but I would like to switch the VFD on and off rather than pulling the plug each time. As far as I can tell the VFD has no on/off.

I have 10-2 wire feeding the power, I am assuming I need to break the two hot lines in. So here are my questions that I need your help with:

1) Is Breaking both hot lines out of the breaker box correct?

2) Is there a simple switch/box that accomplishes the above?

As always I greatly appreciate the assistance and thanks in advance.

As a buddy of mine says "if you can't fix it with a hammer, it's an electrical problem"

millwrong
08-09-2010, 01:15 AM
You need a double pole-single throw switch. You can find it under it's alias; a motor starter switch. Check your switch amp rating.

ftl
08-09-2010, 01:34 AM
The switch should be an off the shelf switch at Home-Depot. When I put in the plugs for my mill and lathe I used a double box with a switch and two 220V plugs. I think the double pole switch (rated at 25A I think) was under $20. If you are not switching it under load you do not need any kind of super heavy duty switch.

Adding the switch turned out to be a great idea as the lathe has a transfomer and pilot light in it that would otherwise always be on.

EVguru
08-09-2010, 05:17 AM
Buy something that describes itself as an 'Isolator' switch. They're usualy rotary action operating over 90 degrees and have holes to put a padlock through.

winchman
08-09-2010, 08:10 AM
"I have 10-2 wire feeding the power...."

Why isn't there a ground wire running to the VFD and the mill?

studentjim
08-09-2010, 08:37 AM
"I have 10-2 wire feeding the power...."

Why isn't there a ground wire running to the VFD and the mill?
You need 10-2 with a ground (bare wire)

Bill Pace
08-09-2010, 09:30 AM
Doesnt take anything complicated/difficult. This is one of radio shacks boxes and a couple toggle switches from Home depot. Put it on a Enco Bridgy clone about 3 years ago.

The factory switch is still functional, but I rarely use it - using the VFD & belt change to give higher speeds when I need it.

http://i22.photobucket.com/albums/b301/pace1980/IMG_0619.jpg

metalmagpie
08-09-2010, 09:46 AM
What VFD doesn't have the capability of switching the motor on and off? I think for motor switching you should use the VFD controls, or maybe switching attached to the VFD control lines. To power down completely, I'd just use a cheap single phase disconnect with Buss fuses available from any electrical supply house. At that point you are only switching the power the VFD is using, so you need a switch which can make or break an amp or two but which can carry 15 or 20 amps steady state. This you can do with nearly anything.

MTNGUN
08-09-2010, 10:14 AM
I would like to switch the VFD on and off rather than pulling the plug each time.
You should leave the VFD powered up 24/7.

Arthur.Marks
08-09-2010, 12:02 PM
You should leave the VFD powered up 24/7.
Why:confused:

Bill Pace
08-09-2010, 12:24 PM
You should leave the VFD powered up 24/7.

???? me too, why??

Falcon67
08-09-2010, 12:41 PM
This is what I use on my 2HP VFD using #12 wire. It is rated for 3HP or 20A, but I don't know if you can get a 10 gauge wire on the tiny screw contacts on the back. Grizzly H8238
http://raceabilene.com/machine/G0519/images/G0519_VFD.jpg

NONE of the two pole switches at HF or Lowes are rated for 3 HP. Source one online. You could use the breaker if it's line-of-sight from the machine, but they are not really designed for on/off work.

Bill Pace
08-09-2010, 01:11 PM
Hey Chris, does this switch on my belt grinder look familiar? ;) Its off a HF wood planer - another instance where the similarities between Grizz, and others, seems very apparent. It ran a 220v 2HP motor and also was rated 3hp also. Was originally black too, I painted it white to match rest of sander.

I go to a local electric supply house for the common toggle switches in higher voltage/amp -- 220v and up to (I think?) 25 amp in a wide variety of pole positions, and price was a reasonable $8-9.

http://i22.photobucket.com/albums/b301/pace1980/IMG_0838.jpg

arcs_n_sparks
08-09-2010, 01:28 PM
What VFD doesn't have the capability of switching the motor on and off?

All do that I have seen. I believe the OP's intent is to switch off the VFD to save power, and/or save lifetime on cooling fans.

john hawkins
08-09-2010, 01:30 PM
As the inverter in stop mode is not doing any work, it is consuming little energey. Leaving it powered up keeps the bus capacitors charged/formed. For extended periods of time it would be best to power it down. Lightning damage? Children? Guest?

MTNGUN
08-09-2010, 01:36 PM
Why:confused:
Why not ?

My VFD's are powered up 24/7, except for power outages.

If this is in a OSHA regulated shop, then the law may require a power disconnect for lockout purposes. Otherwise, HSMers can merely unplug the VFD when maintenance is required.

Seems like there was a thread on this subject a couple of years ago, where someone claimed that powering down the VFD when it was idle actually shortened its life. Dunno if that is really true, and if it is true, I'm not smart enough to explain why. Something to do with one of the parts being rated for so many cycles.

But, it certainly doesn't hurt to leave it powered up.

KiddZimaHater
08-09-2010, 06:54 PM
My VFD's are powered up 24/7, except for power outages
Are the cooling fans running in them 24/7 as well?
It seems like the fans would die from all that constant running.

KiddZimaHater
08-09-2010, 07:01 PM
I have a general duty safety switch leading to my VFD.
Similar to this:
http://www.cosolar.com/assets/squared_fusable.jpg

J Tiers
08-09-2010, 10:42 PM
If this is in a OSHA regulated shop, then the law may require a power disconnect for lockout purposes. Otherwise, HSMers can merely unplug the VFD when maintenance is required.



Cord and plug connected equipment has the plug as a disconnect, no need for any other. Perfectly legal per the US Electrical code. plugs can be locked with plug covers, just as switch type disconnects can be.

wierdscience
08-09-2010, 10:55 PM
http://www.automationdirect.com/adc/Shopping/Catalog/Circuit_Protection_-z-_Fuses_-z-_Disconnects/UL_508_Rated_Non-Fusible_Load_Disconnect_Switches/SD1_Series_Disconnects_(16-40_Amps)/SD1-025-BR

Marc M
08-10-2010, 12:26 PM
I have a general duty safety switch leading to my VFD...http://www.cosolar.com/assets/squared_fusable.jpg
When feeding anything electronic based such as VFD's, I prefer installing a fused disconnect between the device and the breaker. Breakers are rarely sized properly for the equipment they feed and are generally less reliable than a fuse. Fuses can be better matched to the load in both current and time and hopefully, minimize the damage if things go bad. With FleaBay, the cost of both disconnects and appropriate fuses are a cheap way of adding a layer of protection to your equipment. Like insurance, it's something you hope ends up being a waste of money :)

Marc -

EVguru
08-10-2010, 01:31 PM
When feeding anything electronic based such as VFD's, I prefer installing a fused disconnect between the device and the breaker. Breakers are rarely sized properly for the equipment they feed and are generally less reliable than a fuse. Fuses can be better matched to the load in both current and time and hopefully, minimize the damage if things go bad. With FleaBay, the cost of both disconnects and appropriate fuses are a cheap way of adding a layer of protection to your equipment. Like insurance, it's something you hope ends up being a waste of money :)

Marc -

Unless you're using semiconductor rated fuses I doubt they're anything like as fast as a correctly rated (current and time curve) breaker. I've popped the 40 amp breaker that feeds my workshop without blowing an ordinary 13 amp fuse and that's a 'B' rated breaker, not a fast 'A'.

Evan
08-10-2010, 02:13 PM
It is a code and OSHA requirement that all equipment must either be unpluggable within easy sight of the operator or it must have a mechanical positive action switch. That does not generally include toggle switches. Solid state switches cannot be trusted since there is no actual air gap to cut off the power. If a surge appears on the line the solid state switch may instantly fail and the equipment switch on.

I use fused, lockable 30 amp knife switches on my big machines that are hard wired. They are cheap, only $30.

http://metalshopborealis.ca/pics2/shaperpower.jpg

Mike Burdick
08-10-2010, 02:57 PM
Another option...

Get a magnetic contractor and transformer which is usually 24 volts. These can be obtained from a salvage yard for very little money, if not free. Commercial air condition units are a good place to look.

Then... one can wire the machine with a low voltage switch such that if there is a power outage while using the machine it won't turn back on by itself when the power is restored.