FP ok to stall?

[Joe Johnson]

Originally Posted by Tom Line

We learned this the hard way this year.

We tried to use a FP to run a centrifigal fan out of a dewalt vaccuum. It functioned o.k. 1:1 but didn't give us the speed we needed. We geared it up 1:2 and after running 30 seconds wide opened the Fish smoked a bit and thermal-tripped. We thought we had a bad motor since there wasn't that much load on it (it was spinning at a REALLY good clip) so we wired up another and prompty toasted that.

That's how we learned that you don't run an FP at 100% of rated power if you can help it - even if it is not stalled and is still turning pretty darn fast.

Originally Posted by Kevin Sevcik

Seconded! You can't beat them for sheer power. Especially because you actually have the option of running them at 1/2 stall, even if it's not the best idea. You won't run a CIM at 1/2 stall for more than a few seconds before you trip a breaker.

That said, we're using an FP to hold up a ramp this year. We've currently settled on 25% speed as a semi-safe value. We tried 30%, but after a long session of unintentional idling in the pits, the motor was producing some distressing odors. In the interests of my sanity, the students backed it down to 25% and promised to not leave it idling in the pits.

I love data. Nice.

From the above two posts we learn:

1. The breaker is good, but when you have good airflow (due to high RPM of the motor) it is sort of a marginal protection device.
2. 1/3 to 1/4 full stall torque looks to be about the upper limit of high duty cycle applications.

One final clarification. From Kevin: "You can't beat them for sheer power." This is not exactly correct. The CIMs do actually beat them for sheer power (300+ W peak power vs. 200- peak power), but the CIMs are much heavier and much larger (even after you include an extra gear stage to slow down the speedy FPs).

What I intended say is that the FP motors are easily the top motor in the KOPs based on both power per unit volume and power per unit weight measurements.

Regards,
Joe J.