Hypertherm turning off when cutting 9mm

[martinthelion]

Hi guys!

We have a multicam 1000 table with a hypertherm 1250 cutter. When we cut anything below 9mm(using 60 amps or below), the plasma is working great and dandy. But when I cut anything above 9mm to 1/2"(using 80 amps), the cutter keeps on turning off, the circuit breaker keeps on tripping. I mean it cuts the initial holes, but when the long ones are cut, the control will show waiting for plasma arc.

During this, when I check the plasma, the circuit breaker tripped off. I asked the distributor here in the Philippines why was this happening and they couldnt answer me. They just said that they will follow this up to Hypertherm USA, but its been 3 months and still theres no reply.

Any of you guys encountered this problem? oh yeah BTW, once i turn on the breaker again, the fan of hypertherm is roaring like wild, so I have to turn it off and on again just to have it to rest.

If someone could point me to the right direction, it would be greatly appreciated! I tried checking the manuals and technical manuals, but theres no problem with 9mm cutting or more. So I'm guessing theres something with that I havent looked on.

Cheers!
Martin

[cncbasher]

anything above 9mm is max for 100% duty cycle .
hypertherm recomend over that over 10mm to run at 50% duty cycle , so if your cutting for a long period of time it needs time to cool down .

shorten the continuous cutting time and give it a rest between cuts

what you are seeing is the thermal cutout tripping

[jimcolt]

If it was an issue with duty cycle your circuit breaker would not trip. When any Hypertherm system exceeds the duty cycle temperature the DC output for the torch will be interupted....the fan will stay on, and an indicator LED on the front panel will indicate over temperature. When the fan adequately cools the unit down to operating temperature you can run the system again.

If your panel circuit breaker is tripping...then you either have inadequate wiring, too small of a circuit breaker, or a defective circuit breaker. As you cut thicker material, even at a fixed amperage...the system will draw more current (amperage) because the arc length is longer which demands a higher arc voltage.

It is normal for the fan to come on in Hypertherm units once the internal temperature reaches a certain level.....this by no means indicates that you are approaching the duty cycle limit.

I strongly suggest that you ensure your circuit is rated for the power that your Powermax1000 is drawing. If you know your input voltage and whether it is single or three phase...then you can refer to the Powermax1000 operators manual for the suggested circuit rating in amperage.

Best regards, Jim Colt Hypertherm

[WCIS]

You need to be certain the ampacity of the wire feeding the plasma power source is adequate. Since the price of copper is insane anymore this will be the first place one will try to cut corners to save money. Forget the manual and look on the data plate of the plasma power source. This should have the most accurate data for amperage and voltage requirements. Size your wire for 125% of the current rating, i.e. if data plate states 100 amps at the supply voltage you have available then size your wire for 125 amps. The ampacity table I'm looking at states #1 AWG THHN wire is rated for 130 amps.

There's two things to consider when selecting a breaker:

1) They're designed to be continuously loaded at only 80% of their rated load. Meaning if you're using a 100 amp breaker, 80 amps continuous is all it will handle. Therefore, your breaker needs to be rated at 125 amps for a 100 amp continuous load.

2) The inrush rating of the breaker must be considered. For instance, nearly all breakers sold in the US for household use are rated at 10,000 AIC and designed for resistive loads. If you're feeding your plasma system from a residential grade lighting panel, then you need to get yourself an HVAC breaker at the required amperage for your plasma system. They are desiged to handle the greater inrush currents.

Duty cycle is a ratio of run time vs. "rest" time. If it's rated 50% duty, then it must "rest" for as long as it runs. This will usually only be in minutes. So, run one minute, rest one minute. When you get the power problem fixed, the cooling fan will help extend the run time. I would suggest also, that if you find the above reccomendations too expensive, get that breaker reset as quickly as possible to allow the cooling fan to run while the plasma power source is "resting." Otherwise you'll be looking at an expensive repair bill due to failure of the power semiconductors' from heat saturation.

If you want to play, you've got to pay. That's all there is to it.

[jimcolt]

WCIS is correct on all of the electrical points, however in regards to duty cycle...it is far more complicated with a plasma system than the statement below.

Duty cycle is a ratio of run time vs. "rest" time. If it's rated 50% duty, then it must "rest" for as long as it runs. This will usually only be in minutes. So, run one minute, rest one minute.

In reality, a plasma system duty cycle is based on the ambient (room air temperature) temperature, the amperage and thickness of material being cut, as well as the on/off cycle times. The Powermax1000 duty cycle is rated at 50% when cutting 1/2" steel at 60 amps (at book torch standoff and cut speed) at 230 volts single phase, 60Hz input power) with an ambient air temperature of 104 degrees F.

to increase the duty cycle above 50% when cutting 1/2" steel:

- cut in an environment with a lower ambient air temperature.
- operate the unit on a higher input voltage or a 3 phase input power

When cutting on thinner materials, which requires a shorter arc....expect higher duty cycle ratings.

Regardless of the duty cycle issues, the problem that the original poster (martinthelion) mentioned (breaker tripping) is most likely an issue that is not duty cycle related, rather would be a problem with exceeding either the operating current specs of the breaker, or exceeding the inrush specifications of the breaker, or could be a defective breaker.

Jim Colt