Electrical Question

[WillieB]

Last post wasn't in a language I can understand.

20 x 120 = 2400. 2400 watts won't generate more BTUs than can be dissipated in a machine calibrated for 240 Volts. Manufacturer doesn't worry about exceeding duty factor supplied at 115 volts. In that case, the circuit will trip before machine gets hot.

I'm going to buy a new Corvette. I'm too cheap to pay for it, so Chevrolet offers a Corvette with a lawn mower engine. No, it won't perform as designed, but you bought it because it was cheaper. Now, you want a Corvette? Dig up the money for the correct engine.


Transformer welders are power hogs! If you don't have enough power they don't work as well as designed.
Inverter welders use less power, they are adaptive to voltage loss. If supplied with less voltage, they compensate with higher amps. Higher amps causes higher losses in voltage. In some cases it isn't enough power.

There are the auto body welders. They will NEVER want to weld anything thicker than 20 gauge steel. 999 out of every thousand welders will at some time want to weld heavier metal. Some might want to weld aluminum. The cheapest possible outlet will NOT support any exploration, or upgrade.

I never said your mini welder has to have the same power source as my Lincoln 400, but consider how far those electrons had to travel to get to your 50 foot circuit. It ain't ALL about the circuit. There is voltage loss in every link of the chain even before it reaches the circuit. Whether Transformer, or inverter, your welder will not perform at peak supplied by undersized wire.

Not brain surgery, basic algebra. Transformers want designed voltage, Inverters want equivalent available wattage, they adapt (within limits) to low voltage by higher amps.

For good reason, we figure Ampacity. Ampacity is where a failure causes fire. It is rare that a welder circuit exceeds its ampacity.

[Sberry]

I understand what you are getting at about the numbers. Here is the minor difference in issue or method so to speak. I think the breaker trips when the load is exceeded for sure but the machine has its own thermal. It will shut down if the duty is exceeded without tripping the breaker. Consider the 240 models,, wont trip but will shut down on internal thermal. I also understand its sort of semantics but its kind of about how they get there I guess. Breaker shuts down if input is exceeded too long, internal thermal shuts down if output or machine is overheating?

[Sberry]

I wanna get a pic on the label of my hoist motor. Maybe you can help me understand it a little better.

[Sberry]

i might have to get better pic, i have to go for while.

[WillieB]

I understand what you are getting at about the numbers. Here is the minor difference in issue or method so to speak. I think the breaker trips when the load is exceeded for sure but the machine has its own thermal. It will shut down if the duty is exceeded without tripping the breaker. Consider the 240 models,, wont trip but will shut down on internal thermal. I also understand its sort of semantics but its kind of about how they get there I guess. Breaker shuts down if input is exceeded too long, internal thermal shuts down if output or machine is overheating?

I'd be surprised if the internal thermostat is disabled, but on a 2400 watt reacting circuit, thermal overload isn't likely going to be reached.

[Sberry]

I have to get a better picture of the label . I got a question about the nature of the protection. Says motor not externally protected. I dont see it internally protected. Says the breaker needs thermal and magnetic,, well duh but a breaker isnt going to provide motor protection at that high rating? I have the single phase model.

[WillieB]

NEC offers exemptions for fractional horsepower motors. Otherwise, NEC requires thermal overload protection. Many choose the "I don't need to be inspected" loophole.

If a motor doesn't have internal overload protection, it needs external thermal overload protection.

In the old days we used "heaters", thermal overload devices. They were a solder pot surrounding a shaft. A heater surrounded the solder pot. As amperage increased, the incandescent heater got hotter. Melting solder allowed the shaft to rotate. a trigger moved & tripped a switch.

They are expensive. Some go Amazon, find cheap ones.

[Sberry]

I was wondering if there was some implication that additional equipment needed to be installed. The switch is operator held so the real danger is minimal but the language left me wondering and seems I have heard the question on other forum. Mohawk is a big outfit, seems I read the manual also and dont recall it. They send a plug and recept with each unit, only thing is they use the same 3 ph twist lock for all.

[ryanjones2150]

Sounds similar to the overload protection in a motor starter. I have two or three of those laying around I took off machines when I installed variable frequency drives. Same idea you’re talking about, Willie, for an external overload? They have both the magnetic coil and thermal fusible links.

[WillieB]

I was wondering if there was some implication that additional equipment needed to be installed. The switch is operator held so the real danger is minimal but the language left me wondering and seems I have heard the question on other forum. Mohawk is a big outfit, seems I read the manual also and dont recall it. They send a plug and recept with each unit, only thing is they use the same 3 ph twist lock for all.

Industrial motors seldom have internal thermal overload protection. Sometimes it's built into a magnetic motor control. Older motor controls had "melting Alloy Relays. Newer, usually adjustable magnetic sensing relay. They interrupt the electromagnet coil in the controller.

If you have anyone looking over your shoulder, Electrical Inspector, insurance inspector, OSHA, or you just don't want the liability, you need some form of thermal overload protection. I'd go with the magnetic motor control. You can mount panic stop buttons anywhere you might need, & it'll stop in the event of a power interruption. Machines that restart without human control are a concern. Another value is these react to imbalance & shut down protecting the motor from disaster.

[WillieB]

Sounds similar to the overload protection in a motor starter. I have two or three of those laying around I took off machines when I installed variable frequency drives. Same idea you’re talking about, Willie, for an external overload? They have both the magnetic coil and thermal fusible links.

Yes, The "melting alloy relays" are not actually relays. They are rotating shaft with a cog wheel. Wrapped around the solder pot is an electric heater. Too much current, heater heats up, melts the solder, allowing a dog under spring pressure to rotate the cog wheel. This is a trigger switch turning off power to the electromagnet.

Kind of a nuisance, each motor needs a different size units, they are expensive, and few suppliers have them to sell these days. I favor the Current transformer units, nothing extra to buy.

[Metjunkie]

Willie, you just brought back a lot of memories. When I was still amongst the working, I spent many years as a factory maintenance mechanic in a facility built in the forties. They had many pieces of equipment serviced by those old "heater" equipped starters. Even though it's old tech by todays standards, I always marveled at the ingenuity of the folks that came up with that stuff. We had numerous bins of heaters of different ratings. Good times!

[ryanjones2150]

You ain’t kidding about them being expensive. When I installed my Bridgeport, the one that was on it was in rough shape. I had to get three different used ones to get all the right parts. The first used one had the wrong coil but the right fusible links. The second had the right coil and the third had an intact reset button. I traded some aluminum welding for two of them and Don helped me work out the right configuration.

When it came time for my big, old pedestal grinder install and the motor starter was beat up, I just went with the VFD instead. So if any of you guys are looking for some square D motor starter parts, I may have what you’re looking for.

[Sberry]

ok, a pic. I should have been more square but I happened to be looking for some drive roll stuff and this caught my attn. This is an older machine. Looks like they have at least 5 means of thermal before the breaker would even come in to play. One set of thermostats for general but also a set of overcurrents in case the thermals do not react fast enough.

[Sberry]

This was kind of the point from the beginning when I read a blanket statement like,,, the breakers job is only to protect the wire in the wall from overheating when it actually doesnt on this type of circuit. The wire is simply sized sufficient not to be overloaded and the breaker provides short circuit but must be large enough to let enough current to pass. They size wire by duty cycle more than breaker size. Slightly different than a general circuit can be overloaded from multiple receptacles.
I see a bit of the reasoning the IBC doesnt allow multiple 240 outlets on one circuit above 20. Done correct not a problem, wrong and we have an overheated wire from multiple loads. .