Larger Power Cord for a Cutmate 375

[johns6]

I have read where this machine will benefit from a larger power cord. It comes with a 14-3 cord so I assume 12-3 or 10-3 would be better. What benefits can I expect if any? What I really want to change is the ground cable. It is just a stiff little wire that really looks cheap on this cutter. Come on Miller, this is a corner you really don't need to cut. If I had seen the machine with the dinky little ground wire I would not have ordered it.

[HAWK]

johns6,

I hate to hear you are dissappointed in your Miller Cutmate 375. If you will compare ground cables on plasma cutters, you will find they are typically smaller than the ground cables on welding power sources. Some of the Thermal Arc machines have a pencil sized ground cable with an alligator clip on the end. It does a good job regardless of looks.

Take a look at this thread concerning plasma cutters. dmillers post is of specific interest to you. He mentions changing the power cord and transforming the 375 in to a brand new cutting machine. I think the 4 or 6 gauge cable he used is overkill. I would try an 8 gauge so cable. There are several manufacturers of SO cord so shop around and locate a good flexible cord for your input power. Carol is a manufacturer that makes a good SO cord.

Let us know how the power cord upgrade affects the cutting capacity and quality of your Cutmate 375.

[johns6]

Hawk, not really disappointed. Just seems like the ground wire is a little on the small side. I especially don't like the stiffness of the wire. It would just seem a lot nicer if it had the same ground cable as the 625. Anyways thanks for the reply. Also read the post you referred me to on the power replacement. Very interesting but I think maybe I should have gotten a 625 after your're remarks on the 375.

[johns6]

I'm already running in on 240 and a 30 amp breaker.So I might just up it to 10-3 wire and put on a heavier plug. My plug now is rated 20 amp. Per owners manual Miller only recommends a 15 amp minimum breaker on 240, so maybe I won't see any benefits in output performance. Thanks for the help.

[HAWK]

rain252,

I must agree with everything you are saying. I only wonder why dmiller had such a performance increase with the 375 when he went to a larger cable? Perhaps it was fed by a 40-50 amp circuit or it was a fluke of sorts.

I had an incident when testing a DVI 175 where I saw a huge increase in machine performance on a particular input circuit. I did not change the input cord to the machine. I used a supply circuit with a 2' run of 6 gauge wire from the 50 amp receptacle to a 50 amp breaker. There was a 65' run from the receptace to the machine on a 4 gauge so cord. The DVI performed outside the rated specs where it would not before. It really does not make much sense, but it happened. Your thoughts?

[HAWK]

johns6,

The 625 is a nice machine. I am very impressed with its ability to crank out 1/4" material with ease day after day. My buddy took his 625 and put it on a PC controlled cutting machine. It is doing a good job for him. I still have a 2050 and it performs well for me in the 1/2"-3/4" category.

How long have you had your machine? Is there a chance your dealer would let you trade up to the Spectrum 625?

[Trap Doctor]

Hawk,

Will your 625 torch head arc 2" off the metal the ground wire is attached too? Does the 625 have a nose cone cap that holds the tip off the work piece at a certain height?

Thanks
jim

[johns6]

Out of curiosity I called Miller and asked them about a power cord change. I was told point blank that whoever told me this didn't know what they were talking about and I wouldn't notice a bit of difference. Just thought everyone would like to know Miller's stance on this

[rb455ho]

I agree with rain. A 3 wire #10 dryer cord is more than adequate. In actuality voltx amps are apparent power rated in voltamps. One must include the cosine of the phase angle between voltage and current phasor to get watts. (line voltate) x (line current) x cos(phase angle) for real power in watts. The cosine of the phase angle is called the power factor and can also be used for determining efficeincy. Use the sin(phase angle) x apparent power to get Q=reactive power from inherent capacitance or inductance. Has little to do with question but off on a tangent.

[Scuppers]

Out of curiosity I called Miller and asked them about a power cord change. I was told point blank that whoever told me this didn't know what they were talking about and I wouldn't notice a bit of difference. Just thought everyone would like to know Miller's stance on this

Doesn't surprise me, johns6. I commented to you in another thread that I thought the Spectrum 375 has a switch-mode boost converter at its input. A boost converter is an active circuit and, as such, can compensate for variations in the input voltage.

More specifically, it can change the duty cycle of the switching device dynamically in response to changes in the input voltage (for example, because of supply wires with relatively high resistance/impedance) so as to keep its output voltage relatively fixed. (NOTE: I'm not talking about the duty cycle of the machine; I'm referring to the duty cycle of the switching device, typically a power MOSFET, BJT, IGBT, etc.)

In contrast, a passive device, such as a buzz box, is at the mercy of the variations in its input power. For example, if the input voltage is less than its nominal or rated voltage (e.g., because of relatively thin and/or long supply wires), the buzz box has no inherent ability to compensate. Consequently, its output power and, hence, its performance, may suffer. As such, it may benefit from beefing up the supply wires.

As another benefit, a boost converter can correct an otherwise low power factor and therefore use input power more efficiently. A power factor of 1.0 corresponds to a purely resistive load, which uses AC power more efficiently than reactive loads that include inductors/capacitors. The boost converter, used with an appropriate feedback circuit, can vary the duty cycle of its switching device so as to draw a nearly sinusoidal current from the supply. As a result, the utlity grid "sees" a power factor close to 1.0.

Probably more than you wanted to hear, but I would hate to see you spend a lot of time/money on probably unnecessary upgrades.

[rb455ho]

Rain,I do not have to. Scuppers did a great job!!!

[HAWK]

Hawk,

Will your 625 torch head arc 2" off the metal the ground wire is attached too? Does the 625 have a nose cone cap that holds the tip off the work piece at a certain height?

Thanks
jim

Jim,

My buddy has the 625 and I have the 2050. I am not sure how far the arc will jump, but I can get back to you on that tomorrow. If you are referring to a drag cup that creates a .125" stand off while dragging the cup against the work piece, then yes the 625 and 2050 both have that feature. There is also a standard tip that you must hold at the desired stand off distance. It is really nice for work in tight spots.

[Sberry]

This machine shoould not be use on circuits above 30A. We might ask Miller engineering whether it would be acceptable with cord changes but I would suspect the internal wiring isnt designed for it. It came with a 14 cord, maybe they would allow for 50 with a 12 cord?