The plasma cutter duty cycle of a particular unit is the amount of time in an hour the cutter can safely operate without the torch or unit overheating or shutting down. This is generally expressed as a percentage and is determined by how much amperage the unit draws. Let’s say the plasma cutter you are looking at is the Hyperthem Powermax 45 and it has following duty cycle values:
|50%||45 A, 200 – 240 V|
|60%||41 A, 200 – 240 V|
|100%||32 A, 200 – 240 V|
So when making an average cut on a half inch thick metal that requires 45 amps of power, this Hypertherm plasma cutter can run for about 30 minutes every hour without overheating (50% of an hour). Similarly, it can make cuts requiring 41 amps for 36 minutes out of every hour (60% of an hour). Finally, for cuts requiring 32 amps or less, this unit require no cooling time. (Note: Make sure to check out your manufacturer’s cut guides for proper amp requirements so you can evaluate duty cycle correctly).
So why is duty cycle important?
This importance of a duty cycle depends on how you will use your plasma cutter. Ask yourself: “What types of jobs will I be using my plasma cutter for and the thickness of metals I will commonly be cutting and where will I be cutting?” In general, a higher or longer duty cycle comes with larger power requirements and a larger price tag.
If you are performing long, time-consuming cuts or are cutting in an automated set-up such as a CNC type of setup, starting/stopping or downtime is costly. If you are looking for a plasma cutter for your fabrication shop, you might require a duty cycle of 50% or higher for production purposes. So a plasma cutter with a larger percentage at higher amps, will mean that you are cutting more and therefore, making money and have less idle time.
However, if you’re using your plasma cutter for shorter periods of time, such as on small jobs, artistic jobs or just general cutting, the duty cycle might be less important for your needs. If you are a home user or an occasional user, you might easily get by with a model that has a 35% duty cycle at the same rated output.
Additionally, the plasma cutter duty cycle is based around a defined speed of cutting. The manufacturer typically provides cutting speeds for all thicknesses of metals. This is measured in IPM (inches per minute). If the metal you cut most frequently is say ¼”, a machine that offers a higher amperage will be able to cut through the metal much faster than one rated at a lower amperage, although both will do the job. For production cutting, a good rule of thumb is to choose a machine, which can handle approximately twice your normal cutting thickness. The thicker the metal, the higher the amperage required and that impacts your duty cycle.
There is another important factor to take into consideration for the duty cycle that most don’t talk about—ambient temperature. A duty cycle is usually given for the maximum output of the unit (typically at 104F (40C). The ambient temperature can impact the duty cycle. Let’s say the unit has a rated duty cycle at 75F (24C). It will not be able to run that same percentage with the temp is at 95F (35C). However, the reverse is also true, as it could run a bit longer if it was operating outside at 40F (4C).
So the plasma cutter duty cycle is the amount of time in an hour the cutter can safely operate. Knowing how you will use your cutter in relation to duty cycle is important because, if you go over your duty cycle, you risk damage to your plasma cutter or you get to take a break while the cutter cools down.