PDA

View Full Version : Need some electrical advice please!



torker
07-24-2008, 07:26 PM
Hey guys!
I just got my ironworker motor all hooked up and running!
BUT..I "sorta" cheated... The magnetic starter reads... for 110V good for 1hp.
For 220V..good for 1 1/2 hp.
For 460V...good for 3hp.
I've got a 3hp motor...hooked up to 220V
I didn't think I could get away with it but it fired up and worked fine...for about 5 minutes then the motor shut down(the mag switch kicked out).
I'm assuming it was the mag starter overheating???
Can I replace something in the switch or do I have to buy a bigger one?
Thanks!
Russ

Richard-TX
07-24-2008, 07:46 PM
The overload heaters finally kicked out.

Time to upgrade to something a bit more suitable.

Get a new contactor and overload suitably rated for the motor.

IEC contactors and overloads are cheap. Factorymation.com is one of many suppliers.

New contactor and overload should cost less than a tank of gas.

torker
07-24-2008, 07:54 PM
The overload heaters finally kicked out.

Time to upgrade to something a bit more suitable.

Get a new contactor and overload suitably rated for the motor.

IEC contactors and overloads are cheap. Factorymation.com is one of many suppliers.

New contactor and overload should cost less than a tank of gas.
LOL! A fill up here is $200 now!
So what you mean is I have to buy a whole new switch?
I'll have to look on my other mill. It has a mag starter that may be heavier.
I run it thru the VFD now so I don't use it.

Carld
07-24-2008, 08:09 PM
You may find a 3 hp motor starter on the internet somewhere used reasonable. I don't think putting bigger heaters on it will raise it up to handle 3 hp.

torker
07-24-2008, 08:16 PM
OK..Thanks! I'll just have to bite yet another bullet with this thing. I don't mind tho...money well spent!

JCHannum
07-24-2008, 08:16 PM
If you are using the single phase motor you bought for the ironworker, you do not need a magnetic starter as such. A plain motor minder single phase switch will work. (I wouldn't begin to think of telling you to simply bypass the heaters.)

torker
07-24-2008, 08:22 PM
Jim, I'm pretty sure Workers Comp would require a mag start on this.

JCHannum
07-24-2008, 08:28 PM
Jim, I'm pretty sure Workers Comp would require a mag start on this.
I don't know the code there of course, but it is no different than an air compressor or any other machine with a single phase motor on it. It does not require a starter as it is capacitor start.

You should take a good look at wire sizes though, they can be considerably smaller for 460, and might need replacing for the 220 motor.

torker
07-24-2008, 08:34 PM
Jim..they didn't cheap out on the wire. It's all 10 guage.

JCHannum
07-24-2008, 08:38 PM
Jim..they didn't cheap out on the wire. It's all 10 guage.
All good there. I just had the second thought on that. Manufacturers are good at that, build just to meet code and nothing extra.

Richard-TX
07-24-2008, 10:10 PM
LOL! A fill up here is $200 now!



To put it in real terms a 22 amp contactor is $22.00.
A 22 amp overload is $16.00

I would replace them both.

http://www.factorymation.com/s.nl/sc.2/category.11600/.f

Maybe a fill up on your lawnmower.

wierdscience
07-24-2008, 10:36 PM
Russ,5HP 220vac 1~ air compressor mag starter,costs around $110 including the box,NEMA rated.Order the heat strip sized for your load,then all you need is a push button station.

If your workman's comp is like ours you will also need a disconnect switch within 10 feet of the machine.

DR
07-24-2008, 10:41 PM
I suspect a mag type starter would be required by the worker's comp people. Especially on a machine that can cut fingers (and worse) off.

The idea being, that if you have a power outage while using the machine , when the power comes back on the machine wouldn't start back up by itself.

Fasttrack
07-25-2008, 12:29 AM
That seems silly... they are still lever operated and have so many gaurds and shields that even if it did "turn itself on" after a power-outage, its unlikely that anything would go wrong. Not like a lathe or mill where spinning pieces are exposed!

I found some pretty cheap solid state relays for 10 horse on http://www.surpluscenter.com/electric.asp

Not sure what shipping would be like going into Canada though.

torker
07-25-2008, 12:39 AM
That seems silly... they are still lever operated and have so many gaurds and shields that even if it did "turn itself on" after a power-outage, its unlikely that anything would go wrong. Not like a lathe or mill where spinning pieces are exposed!

I found some pretty cheap solid state relays for 10 horse on http://www.surpluscenter.com/electric.asp

Not sure what shipping would be like going into Canada though.
I'm sure their concern is the "automatic" return stroke. If the power got cut and it was on return it could cause you to get your head cut off...cuz I ALWAYS stick my head inside machines after a power bump :D

Fasttrack
07-25-2008, 12:59 AM
...cuz I ALWAYS stick my head inside machines after a power bump :D


Naturally - its the smart thing to do after all. Make sure everything looks ok and is still operational... :D

torker
07-25-2008, 01:11 AM
Naturally - its the smart thing to do after all. Make sure everything looks ok and is still operational... :D
Ah.. you do it too huh? :D

JRouche
07-25-2008, 01:30 AM
Haaa.. Thats why they have mag starters on the industrial equipment? Im always learning. I just thought it was for fire and motor protection.

Too bad you have to deal with the OSHA equivalent. And if thats yer only reason then you need to do the "correct" thing for insurance purposes.

Guess I would look at it like any other single phase tool. They arent covered like three phase tools. Even though the single phase saw (or press) would be ok for the home owner to run without re-start issues. Kinda funny, they wanna "protect" the workman in the shop but homeowners with the 10 inch saw is ok. LOL

So, cause you have BB looking at the whole operation I say do it to their liking. If they werent there I would not use a mag starter and heater setup for that rig.

I would run it like the 10 inch table saw with an on and off switch.. JR

Fasttrack
07-25-2008, 02:03 AM
Mag starters are used on 3-phase to insure that the motor is energized simulataneously by all three phases. Thats why JCHannum said that a mag starter wasn't neccessary since it is "capacitor start". The capacitor acts to "split" the single phase in. It allows the run coil and start coil to experience two different instantenous voltages. (The rms value is the same, but the capacitor "splits" the phase so if you think about a sine graph, one is shifted over slightly). This difference is what creates the start-up torque in a cap start motor. Since there is only one phase and the phase off-set is determined by a capacitor, it doesn't matter when you turn on the switch.

With three phase machinery, if you throw a mechanical switch but it closes two phases faster than the third phase, you'll fry your motor since its designed to operate with the three phases being... well "in phase" with each other. A motor disconect box could theoretically be used as a 3-phase motor control except for safety issues, but you will sometimes see old disconects that don't close simultaneously and subsequently destroy motors.

torker
07-25-2008, 07:56 AM
I was thinking about this last night. I don't have any employees to worry about now so I'm just going to wire this up with a "table saw" switch for now. If and when "they" tell me I have to have a mag switch...then I will put one on it. I'm sure they'll find lots of other infractions here in Hillbilly Hollow anyway :D

Dawai
07-25-2008, 09:57 AM
IS there a "overload " button on the motor??

Usually a red push button on the end.. sometimes painted over.

If so, you just need a switch to turn it on.. and appropriate fuse or breaker protection for short circuits.

Russ:
I'm getting your dc motor boxed today. I really am.. I really am.. really.. I just tore down about two dozen boxes I emptied motorcycle parts from in the dining room. still sweeping lil white peanuts and pieces..
I got the perfect cardboard box laid out..

Still don't know what to do with the four bags of shipping peanuts thou..

ckelloug
07-25-2008, 10:02 AM
If there is a Mailboxes Etc store where you are, they will accept peanuts for reuse.

Richard-TX
07-25-2008, 11:31 AM
IS there a "overload " button on the motor??


Two points that I feel need to be mentioned here.

1 - I have yet to see any 3 phase motor that has an integral overload.

2 - The overloads on 1ph motors aren't all they are cracked up to be. I have seen 1ph motors burnt to a crisp yet the integral overload never tripped.

Paul Alciatore
07-26-2008, 02:10 AM
Mag starters are used on 3-phase to insure that the motor is energized simulataneously by all three phases. Thats why JCHannum said that a mag starter wasn't neccessary since it is "capacitor start". The capacitor acts to "split" the single phase in. It allows the run coil and start coil to experience two different instantenous voltages. (The rms value is the same, but the capacitor "splits" the phase so if you think about a sine graph, one is shifted over slightly). This difference is what creates the start-up torque in a cap start motor. Since there is only one phase and the phase off-set is determined by a capacitor, it doesn't matter when you turn on the switch.

With three phase machinery, if you throw a mechanical switch but it closes two phases faster than the third phase, you'll fry your motor since its designed to operate with the three phases being... well "in phase" with each other. A motor disconect box could theoretically be used as a 3-phase motor control except for safety issues, but you will sometimes see old disconects that don't close simultaneously and subsequently destroy motors.

Does this make sense? I am referring to the second paragraph: frying a three phase motor by running it on two phases for a split second. There is little mechanical difference between the contacts in a mechanical switch and in a mechanical relay ("contactor" is just another name for a heavy duty relay). The only difference is where the actuating force comes from: the relay or contactor is driven by a magnetic coil while the switch is driven by a human hand. But both would be subject to the same mechanical tolerances and wear factors and could originally have or develop fractional second sized differences in the closure times of the three sets of contacts. Both are designed with rapid make and break times in mind and the switch may be even faster in this regard as there is usually a toggle action that relays or contactors normally lack.

Three phase motors often run on two phases for much more prolonged times when a fuse for a single phase blows. I have seen this in unattended equipment where the motor ran without any permanent problem for days or even weeks on two phases. Of course, it is not desirable to run this way and there will be some overheating that could burn a motor up or damage it over time. But I have never seen a motor burn up in the fraction of a second that would be produced by contacts "making" a bit slow.

I suspect that contactors are used for larger motors because switches that are capable of handling the higher Voltages and currents would have a number of undesirable characteristics for panel mounting. These characteristics would include larger size, difficulty of adding features like indicator lamps, and additional safety factors like insulation and protection against high current failures like melt downs in close proximity to the human hand. Also, controls may need to be placed a considerable distance from the motor and this would mean running the full Voltage and current two ways back and forth with heavy gauge wires and higher Voltage insulation. It is a lot easier, safer, more efficient, and cheaper to place the contactor near the motor and run a lower Voltage and current control circuit to the control panel. Of course, there is the safety aspect of assured shutdown in the event of a power failure and subsequent restoration but I suspect this was only a later discovery and not the original motivation for the use of contactors. Even motors for mechanisms that are completely isolated from human contact commonly use contactors for some or all of the above reasons.

I know that in the present times, some motor controls use electronic relays or contactors and these devices would completely eliminate any switching latency problems, but the use of motor contactors predate these solid state devices by many decades if not a century or more. So please do not cite solid state, electronic contactors to disprove my arguement.

If I am missing something here, please do inform me.

torker
07-26-2008, 09:06 AM
All this stuff is way over my head! So.. I bought a 3hp rated toggle type switch...hooked it up and the thing works fine.
Someday I'd like to find an "Electrical Stuff For Dummies" book! :D
Thanks!
Russ

JCHannum
07-26-2008, 10:15 AM
The toggle switch is all you need for that motor.

While a three phase motor will run on two phases without damage (think RPC here), it may or may not self start on two phases, and has a 50/50 chance of running in the desired direction. If not given a spin, a three phase motor may start and run in either direction, or "single phase" which is to sit and rock back and forth without making a full revolution. This will cause a motor to burn out in short order.

Once a three phase motor is running, one leg can be dropped out and the motor will continue to run, but at reduced power. (Think static phase convertor.)