CONTINUOUS Power

This was recently posted and several questions arose, mostly around the power. 56 HP 100% duty cycle continuous, some have asked about the S6 and the S1 and what is the difference.

First, in my previous life, I worked for a major motor manufacturer for 5 years. Some terminology falls into the grey areas, but black-and-white charts help reveal facts.

It is my understanding when S1 or S6 is stated, this refers to the duty cycle. An S1 is 100% duty cycle, or this power can be pulled 60 minutes per hour. S6 means an intermittent duty cycle or 60% percent of the time - another way to look at this is the motor needs to rest 24 minutes every hour. This rating is looked at when interrupted loads, maybe on a mill that is tapping a hole, etc.

The above chart is in metric, which can be converted. The power graph shows the maximum power is reached around 100 RPM. "Power S1 1 gear" is 41 kW which equals 56 HP for continuous power. "Power S6 1 gear" shows 84 kW or 114 HP for 36 minutes per hour.

To further interpret this graph, the motor reaches full power at around 100 RPMs, 56 HP continuous, and 114 HP S6 rating. The 2-range automatic gearbox shifts around 275 RPM. Due to bearing sizes, the bigger the bore, the slower the maximum speed. A machine with a 360mm (14.1") bore tops out at 500 RPM, 320mm (12.5") runs up to 700 RPM and the 220 mm (8.6") bore runs up to 1,000 RPM.

Understand anything less than 100% continuous cycle needs to rest. When spindle power is quoted, don't be afraid to ask the rating if it is not spelled out.