Replies

1. 
   DavidThomas | Dec 21, 2004 01:21pm | #1

   If it is over 1 hp, the "switch" is called a motor starter and it has over-current protection. Basically an overgrown 3-pole relay. Coil voltage is either 120-volt or 220-volts and is such a low wattage you can switch it with anything (standard light switch, for instance).

   Presumably you want the switch to be "latching" and you can do that with the standard light switch very easily. Or you can set it up like a lot of table saws with one push button for start (a momentary switch, normally open) and a separate one for stop (a momentary switch, normally closed) The wiring is a bit trickier for the two switches but easy enough to follow a diagram.

   Yes, I have a bunch of them laying around. I'm next in PDX at 6 am on Jan 15th on my way to a toxic waste site in California. You want me to send it? Got the nameplate amps off the motor? The relay part is wide-ranging but the over-current is for a particular amperage range.

   David Thomas   Overlooking Cook Inlet in Kenai, Alaska
1. 
   skyecore | Dec 22, 2004 09:13am | #4

   wow! thanks for the info! Let me see if i understand this correctly and please pardon my ignorance with electricity:

   with a motor starter, i still need a switch right? and is that where i can hook up any old switch (such as a 115v lightswitch)? What i need it for is a rockwell belt/disc sander which had a (i think its called) 'low voltage switch' (cant remember what its called egzactly) but it has a box on the side, kind of looks like a breaker box. The power comes from the wall, into a phase converter(single phase to 3 phase), then to this box, then the switch, and then the motor.The box has gone bad but the switch still works, however (ive been told that) I cannot hook the switch directly to the motor because the switch is low voltage..Can I use the old switch with the motor starter? question two: what does "latching" mean?-->

   measure once

   scribble several lines

   spend some time figuring out wich scribble

   cut the wrong line

   get mad

1. 
   BillHartmann | Dec 22, 2004 10:17am | #5

   If you get a manual starter like the ones at the bottom of the page the control switch is built in.https://www.farmtekcatalog.com/details.cfm?product_name=MR2240The other type of start is a contractor or relay based.They require two monentary switch. A N.O. Start pushbuttom switch which applies power to the coil. And auxillary contact on the relay is also wired to maintain the power on the coil after the start relay is released. That causes the relay to latch on.The power to the control relay is also feed through the N.C. stop pushbuttom. When the Stop is pressed it kills power to the relay and drops out.You can get coils for 24 volts, which is "low voltage", and requires a transformer. Or you can get them for line voltages of 120/208-240/480.

2. 
   Sphere | Dec 22, 2004 03:12pm | #6

   try choking it, lock the throttle full on and pull the rope. That'll be easier. 

   Spheramid Enterprises Architectural Woodworks

   Repairs, Remodeling, Restorations. 

    

    

3. 
   DavidThomas | Dec 22, 2004 09:41pm | #7

   Yes, with a motor starter you still need a switch.  Most switches you throw by hand are one pole (single-phase) and 20 amps or less.  Motor starters connect all three phases at once and are activated by a much smaller amperage to their coil.  That could be provided through a light switch.  Or you could use the switch already on the sander.

   As Bill mentions, those coils can be had in 24 volts, 120 or 220 volts.  The smaller current of that coil voltage is what passes through the hand switch(s).

   "latching" means it stays on without you continuing to hold the switch.  Like a light switch.  Unlike a doorbell - a doorbell only rings when you push the button.  It is a "momentary" switch, specifically one that is "normally open".  "Normally" means its state with no action or voltage applied to it.  As the doorbell sits there, minding its own business, it is an open circuit not connecting the 24 volts to the buzzer.  When you push it, it closes and connects the voltage to the buzzer.

   Is it possible to post a picture of the "breaker box" that has gone bad?David Thomas   Overlooking Cook Inlet in Kenai, Alaska

1. 
   skyecore | Dec 27, 2004 01:20pm | #8

   hope youre still there, i had a pretty busy holiday and havent had a chance to check back in.Thanks for the information! So would I be correct in assuming that my "breaker box" is an old style motor starter? does this pic clear anything up?-->

   measure once

   scribble several lines

   spend some time figuring out wich scribble

   cut the wrong line

   get mad

2. 
   skyecore | Dec 27, 2004 01:21pm | #9

   AGH! my pic diddnt upload.. i'll try again-->

   measure once

   scribble several lines

   spend some time figuring out wich scribble

   cut the wrong line

   get mad

1. 
   DavidThomas | Dec 28, 2004 02:09am | #10

   I tried to wipe the dust from the contactor label on my computer screen! <G>  Time for a nap!

   Yes, I believe that is a an old-style motor starter with "heater elements" on the side.  The heaters can hotter as more current passes through them.  When the limit for that element is reached, it opens a switch and opens the motor starter.  The heaters are for pretty narrow ranges of amperage (like 5.2 to 6.1 amps).   A different amp rating required 2 or 3 new heater elements be purchased.  Newer M/S have a wide adjustment (like 2.4 to 8 amps) that you simply dial in.

   Current from the "low-voltage" switch energizes the coil of the contactor, if the heater circuits are happy.

   Contactor (relay) + overcurrent protection = motor starter.  Those heaters are an old-style of over-current protection.  Now it is solid-state.

   But someone who started their electrical adventrues before me might be able to confirm all that and give you more info.

   And what part is bad, again?  The motor starter or the manual switch that energizes the coil?David Thomas   Overlooking Cook Inlet in Kenai, Alaska

2. 
   skyecore | Jan 01, 2005 04:22am | #11

   heh, I did some reserch on the web to see how those old overcurrent protectors work, pretty ingeneus! I couldnt wipe the dumb grin off of my face.The motor starter is the one that has gone bad.. However im not absolutely certain about that. The only reason that I think its the motor starter is that my dad said that he used to put a heat gun on the motor starter for a few seconds and then it would work again. I'm not sure quite how to test the motor starter but the manual switch is on the other side of the machine so i would assume that my pops heat gun trick would not have worked if it were the swich that was faulty.-->

   measure once

   scribble several lines

   spend some time figuring out wich scribble

   cut the wrong line

   get mad

2. 
   BillHartmann | Dec 21, 2004 07:13pm | #2

   What you want is a called a motor starter. It has contacts and also overload protection.

   https://www.farmtekcatalog.com/lg_display.cfm?page_number=278 and through page 281

   You will also need a disconnect switch to power if off when changing the belt or working on it.

   https://www.farmtekcatalog.com/lg_display.cfm?page_number=276

   You can use the circuit breakers if they are within sight.

   Also check the Grisely catalog.

   But if you have any kind of surplus/salvage place with industrial equipment you will often find these cheap.

3. 
   Sphere | Dec 22, 2004 01:20am | #3

   grainger and Mc Master -Carr can hook ya up right quick too.

    

   Spheramid Enterprises Architectural Woodworks

   Repairs, Remodeling, Restorations.