Efficiency

[sabongi]

Guys from Castle, can you post efficiency charts for your motors?

[Pdelcast]

Originally Posted by sabongi

Guys from Castle, can you post efficiency charts for your motors?

I guess I have to ask, what kind of an efficiency chart?

Something like this? Or do you want a full torque/eff curves?


This is from the current production 1515, at 15.4V: Vertical is efficiency, horizontal is torque output in newton meters.

At 200W out, eff is about 80%. At 400W out, eff hits 90% and stays above 90% to over 1000W.

However, be aware continuous output power is not this high -- the motors cannot shed 100W of waste heat for long. :)


These motors are designed for low continuous power, and high efficiency at high (intermittent) output power.

Also, please note that this is running through a gear (our dyno cannot run at 35000RPM) -- so the efficiency is actually a few percent higher.


Patrick

[sabongi]

was thinking about efficiency X RPM, so we can gear properly :D

[Pdelcast]

Originally Posted by sabongi

was thinking about efficiency X RPM, so we can gear properly :D

Hmmm, well motor efficiency can't be plotted against RPM. Efficiency is based on power, which is torque X RPM. You can plot efficiency vrs RPM with a constant torque but that by itself doesn't mean anything for gearing.

Efficiency with no load is zero at any RPM (because no work is being done.) So it only makes sense to measure efficiency on a torque curve.

Gearing shouldn't be based on an efficiency curve anyway -- it should be based on RPM -- and like I said, RPM by itself doesn't have anything to do with efficiency. It only makes sense when you know both torque and RPM.

I recommend that you use Brian's excellent gearing program, you will do much better in the long run. :)

[himalaya]

Good topic. I was always hoping Castle lists more technical data on its website or somewhere else like here in the RCM forum. Lehner as an example, they list full test data for pretty much their every motor product, so that the customers know exactly what the product is capable of. (You know Germans)

There are a LOT nerd-heads love to read technical data. The data is much more persuasive than any word, it makes your product more competitive, makes your customer more confident.

[nuz69]

35 000 RPM = 583 RPS
583 x 1 = 583 watts no? Then 1 on horizontal means 583 watts?
Unless horizontal is kW output? Maybe a little less because of the rpm drop due to load ?
Anyway we love these kind of curves, plz give us more if possible ;) ! For the other Castle motor for example...

[Pdelcast]

Originally Posted by nuz69

35 000 RPM = 583 RPS
583 x 1 = 583 watts no? Then 1 on horizontal means 583 watts?
Unless horizontal is kW output? Maybe a little less because of the rpm drop due to load ?
Anyway we love these kind of curves, plz give us more if possible ;) ! For the other Castle motor for example...

Power is equal to nm * radians per second, not rotations per second.

So you calculate rotations per second time 2 times pi, then multiply by the torque. That gives watts.

[nuz69]

My bad ^^ Let me do this with the old way. A force of 1N at one meter of center, mean the work of this force is :
2*PI*1*1 = 2PI. The power is work / second. In one second, the work is :
2PI**1*1*583 = 1166x PI = 3662,989 J/s = 3663 watts ???

[nuz69]

Unless a heavy drop in motor RPMs like 35000 to ~9000, but I don't think that such RPMs drop is possible, even at 3000Watts.

[maxxximatoze]

Originally Posted by nuz69

Unless a heavy drop in motor RPMs like 35000 to ~9000, but I don't think that such RPMs drop is possible, even at 3000Watts.

Very very old post but I answer just for fun. So I guess...

The magtrol that castle was certainly using for this test is limited to 10Krpm (seen elsewhere a post from Pdelcast in this forum) and the power supply was certainly their sorensen 80A (also seen elsewhere a post from Pdelcast in this forum).

So to get the last point of this graph at 1Nm and 10000rpm, it gives 1047W (10000/60x6.28) of mechanical power, which is 76A at 15.4V and 93% motor efficiency and 80W losses for the 1515 (see http://bavaria-direct.co.za/constants/ with 1515 parameters to verify, with I0 2.7A at 15.4V measured on my 1515, and rm 0.006ohm and so loaded KV at 76A was around 2145 rpm/v due to the back emf at 76A and to 0.006ohm phase)

This was certainly done through a reductor of around 3.3 ratio so the rpm can be reduced from around 33000 rpm at around 0.3Nm to 10000 rpm and 1Nm, which give the same power of aroud 1047W. And like every pinion/spur couples, the efficiency is not 100% but more like 97/98%, so 0.93x0.97 gives around 90% effciency at the dyno.

With these numbers, everything seems pretty coherent.