Power Consumption of Train Motors

[Rob Klingberg]

Hello all, I'm wondering if anyone knows or has measured the peak mA consumption (typical, no load) of each of the Lego train motors:

* 12v motor

* 9v motor

* PF motors

Just curious, thanks!

--Rob

[hoeij]

quote of entire topic removed by moderator -TheBrickster

With no load, a 12v motor draws around 0.20 amp. In my 12V trains, the motors use 0.25 amp,

which indicates that they are pulling a modest load (still, these are 5 feet long trains, but

I've taken steps to reduce rolling friction, e.g., I'm using 9V train wheels instead of 12V

train wheels).

If you try to pull a very long train with a single motor, consumption can go up to 0.50 amp and

probably higher but I did not test it higher than 0.50 amp.

The 9V and PF motors use less. There is a useful website with information that has all

the information for them (just google: LEGO 9V Technic Motors compared characteristics).

There is no overload protection, so there is no well defined peak consumption. I do not

know what a safe amperage is for these motors. But I would not want to subject my motors to

say 0.50 amp for an extended period of time. If they don't get warm, then you know you're OK.

[Duq]

For all 9V motors check out Philo's website for all specs you need:

http://www.philohome.com/motors/motorcomp.htm

[Tearloch33]

LEGO customer service told me that the new PF train motor (88002?) draws less current than the older RC motor, yet has a higher power and torque output. I guess the upgraded the motor itself, making it more efficient. I have not conducted full scale testing, but I do know that the PF motor has much better speed response than the older RC motor, and the battery lasts considerably longer under the same conditions for the PF motor.

[hoeij]

LEGO customer service told me that the new PF train motor (88002?) draws less current than the older RC motor, yet has a higher power and torque output. I guess the upgraded the motor itself, making it more efficient. I have not conducted full scale testing, but I do know that the PF motor has much better speed response than the older RC motor, and the battery lasts considerably longer under the same conditions for the PF motor.

That's correct. The main difference between the RC motor and the PF motor is that the PF motor contains a DC motor of much better quality. So it is stronger, and more energy efficient at the same time. It will probably last much longer too.

By putting in the cheapest motor they could find into the RC train, and putting a better motor into the PF train, they can now correctly claim to have improved the motor.

Hello all, I'm wondering if anyone knows or has measured the peak mA consumption (typical, no load) of each of the Lego train motors:

* 12v motor

* 9v motor

* PF motors

Just curious, thanks!

--Rob

Some time ago I had two 12V trains running on the same loop, and I remember seeing something interesting: Every time when one train goes through a curve, then *both* trains slow down.

What happens is that when one train goes through a curve, then it starts to draw more mA. This extra draw of current causes the voltage on the track to decrease. This, in turn, causes both trains to slow down (the effect is quite significant with the 12V system. It is less obvious with the 9V system because the 9V controller has a regulated output voltage).

In essence, the reason that the train slows down in the curve is not simply "it has to do more work, so that's why it slows down". When a train goes through a curve, the motor starts pulling more amps, that causes the voltage on the motor to decrease, and that decrease in voltage explains most of the decrease in speed.

With the 12V system you can see this very clearly (like I said, when one train goes through the curve, then both trains slow down, including the one that's on the straight track).

If you want to observe this in the 9V system, then make a very long oval (say: 40 straight, then 8 curves, then 40 straight, and 8 curves again). Now connect the power supply in one of the two curves. You'll see that the train slows down in each of the two curves, but it slows down way more on the curve that is far away from the power supply. This is because a long track has resistance (count about 0.08 Ohm per track, so the other side of the track is about 40 * 0.08 / 2 = 1.6 Ohm away). The higher the resistance is, the more of a voltage-drop you'll get with an increase in amps. So the higher the resistance, the more of a speed-drop you get in the curve. An extra 1.6 Ohm is something you'd certainly notice (especially in the lower speed settings).

Edited May 27, 2011 by hoeij