Motor and Controller Power Matching

[joamanya]

Hello, need a little help understanding something.

What will define the power of your system, biocides the battery, lets first asume suppose you have infinite voltage or amps, ok?

Then, If you have a 1000W motor (2000W peak), and you use a 350W controller, will the motor just run at 350W or it will melt the controller because will "drink" the 1000W to work?

Then at the oposite, if you have a 350W motor and a 1000W controller, will you melt the motor? or the system will work just at 350W?

A technical explanation would be very welcome.

Regards!

 

[fechter]

A typical controller will limit the power to a particular level and not go above that. It should be able to run all day at it's rated power. If you mate a 350W controller with a 2kW motor, it will run at 350W and the motor will probably never get warm. You just have an unnecessarily heavy motor. A controller's power rating is based on the system voltage and the current limit in the controller.

In the opposite scenario, if you ran a 350W motor with a 1000W controller, it would be possible to melt the motor. A 350W motor can probably handle well over 1000W for a short burst, but heating will limit how long you could get away with that. A motor's power rating is not so clear cut. It is based on how much it can handle continuously without overheating. Well, this depends on how much cooling it gets and a bunch of other things.

For example, my modified A2B uses a controller that can put out 2500W. The motor was originally rated for 500W. I've added ferrofluid to the motor and made a few other changes, but it's still basically a 500W motor. If start climbing a long, steep hill, the motor temp steadily rises and after about 30 minutes of hammering it, it will get hot enough to be close to the failure point.

If had a 2500W motor instead, I could probably go much further before things overheat. A motor temp monitor is how I keep from melting the motor. Once the temp gets to the danger zone (winding temp 100C), I have to stop and let it cool off.

 

[dogman dan]

If you use a 1000w motor and a 350w motor, it will try to drink all it can, longer than usual for a 350w motor. But it will limit at 350w. Most likely the controller will not fry, but it is possible to cook off controllers. Usually this is done at high wattage, high load, and high rpm motors in big wheels.

But if you limit to 350w using the big motor, it will just run as efficiently as a similar 350w motor. The big motor will pull harder at first, but only for a millisecond or two, then the controller limiting kicks in.

I ran a real big motor at 200w a lot, for maximum range, when the next plug or drink of water was 70 miles. I'd run 15 mph, pulling 200w and pedaling another 100w or so.

How you limit the power doesn't really matter. I just ran with the throttle nearly off, and jammed the grip to set it there for miles and miles. Other times, I have limited power with a Cycle Analyst, because I was using a battery not able to put out 2000w, as the unlimited controller would have allowed. So I'd set amps to limit the controller to 1000w.

 

[joamanya]

Thank you very much for your both answers. I understand Fechter answer is more understandable. So the conclusion is that the controller is which limits the output power, if the motor is too small we will need to be careful with the overheating.

Regards!!

 

[dogman dan]

Hmm, I'll try again more simpler.

If you want a big motor for big power sometimes, you can still run just as efficient as a small motor too, when you want to. You just weigh more.

Big motor given 350w is the same as a small motor given 350w. Both run efficiently, unless its up too steep a hill.

But give the 350w motor 1000w, and you start running hot, and if the run is long enough, it could melt the motor. It will melt the motor if you run up a long enough hill. Takes about 45 min to cook off 350w geared motors, if you run 1000w, and go up very long hills.


Take the big motor and feed it 1000w, and it barely ever gets warm, unless the hill is extremely steep, and very very long.

 

[999zip999]

A motor also makes heat when it luggs or Troggs. Its making heat in sand and going slow in thick mud. For the most part. This gets magnified when you over volt it or over amp the motor .Do you have a 350 watt geared motor ? Geared motor can hoer heat longer or quicker than a 28mm dd motor.