HUB MOTOR CAPABILITY

[mountainsport]

Hi All,
Who can help me understand this question? I'm not sure if this applies also to geared or mid drive motors, I am mainly concerned with the direct drive brushless geared-less hub motor.
How do we know when the motor is under powered for a system or what are the tell tell signs?
For instance lets say a 500watt motor, how far can we push it regarding volts or amps until problems to occur?
Secondly, when people say they have burnt out their motor, what do they really mean by this and how it happened?

Cheers
MS.

 

[Woosh]

you need 600W of mechanical power for 25mph, 1200W for 30mph.
At this sort of speed, your direct drive gearless motor will run very efficiently.
You will need a 1000W DD motor with 36V 35A controller for 25mph performance and 1500W DD motor with 48V 35A controller for 30mph.
500W direct drive motor will not be good for anything because it won't have the power to get to the sweet zone.
Why do you want a DD motor?

 

[flecc]

500W direct drive motor will not be good for anything because it won't have the power to get to the sweet zone.

Hush, you'll be upsetting justebikes.co.uk.

They sell the Dutch Sparta Ion 250 watt Direct Drive motor pedelecs.

They won't like being told they're £2000 worth of useless scrap!
.

 

[danielrlee]

Simple answer: Heat. If it's regularly reaching temperatures of over 100C (winding temperature), you're pushing it too hard and require a larger motor.

When people talk of burning out a motor, they're talking about getting it so hot that the varnish on the windings burn up and the motor becomes a write-off. Another possible failure mode is destroying the hall sensors due to heat. These are fairly simple to replace though.

 

[Crockers]

Hush, you'll be upsetting justebikes.co.uk.

They sell the Dutch Sparta Ion 250 watt Direct Drive motor pedelecs.

They won't like being told they're £2000 worth of useless scrap!
.

Are they useless carp?

 

[Danidl]

Hi All,
Who can help me understand this question? I'm not sure if this applies also to geared or mid drive motors, I am mainly concerned with the direct drive brushless geared-less hub motor.
How do we know when the motor is under powered for a system or what are the tell tell signs?
For instance lets say a 500watt motor, how far can we push it regarding volts or amps until problems to occur?
Secondly, when people say they have burnt out their motor, what do they really mean by this and how it happened?

Cheers
MS.

There have been a number of postings on this topic and while not disagreeing with anything Woosh has said here is another take. An electric motor is just a conduit for converting electric energy into mechanical energy. The electric power going into the motor is the product of voltage and current. The mechanical power output is determined by the efficiency by which it can convert this into torque and rotational speed. Each motor will have been designed to have a speed at which this is optimised. If higher voltage is applied then either and both of more current flows increasing torque and depending on the technologies used, the motor rotates faster .
Typically a motor just consists of three sets of copper wire windings .. coils, the controller directs current to each set of windings in a sequence and this drags the rotor around. If excess current is used it will heat up the wire and the metal parts. Under some conditions the insulation around these windings can melt and the windings fuse together.
The mechanical parts respond to the torque produced and if this gets excessive internal gears get shredded..And bearings overheat. ..

 

[mountainsport]

you need 600W of mechanical power for 25mph, 1200W for 30mph.
At this sort of speed, your direct drive gearless motor will run very efficiently.
You will need a 1000W DD motor with 36V 35A controller for 25mph performance and 1500W DD motor with 48V 35A controller for 30mph.
500W direct drive motor will not be good for anything because it won't have the power to get to the sweet zone.
Why do you want a DD motor?

That's great Woosh, but what happens when a system is over powering the hub motor, what will be the outcome of the state of the motor?

 

[flecc]

Are they useless scrap?

Far from it, they are some of the most beautifully designed and built pedelecs in existence. Their quality and that of their sister Koga pedelecs is outstanding.

Not very powerful and best suited to Dutch conditions at introduction, they now claim much higher torque though I think they somewhat exaggerate that.

For a rider in an undemanding area where no hill is over 10%, a good way to spend £2000. But my comments are restricted to the bikes with the Ion rear wheel DD hub motor. They make a few front hub motor bikes with a motor I know nothing about.
.

 

[Deleted member 4366]

When people burn out their motors and controllers, in most cases it's because they went too slow , which can be because they didn't give their motor enough power. Different motors are wound for different speeds. you can have 500w DD motors that climb like a goat with minimal power. Look at those electric scooters. They don't even have pedals to help them on the hills There's no exact answer to the question, You have to consider many things at the same time. Winding speed is fundamental, then there's torque. bike speed, output power, weight, incline, volts and current all affect it.

Never buy a motor unless you know it's winding speed. Once you know that, you can estimate everything else.

If you're thinking of a new bike, Mountainsport, tell us what you're trying to achieve. Maybe we can recommend something.

 

[Woosh]

That's great Woosh, but what happens when a system is over powering the hub motor, what will be the outcome of the state of the motor?

danidl has already answered that question. The motor can't function efficiently, excess energy is converted to heat which kills one of the three SS41 hall sensors.As soon as this happens, the motor will stutter and stops.

 

[Woosh]

Look at those electric scooters.

they have 12" wheels - that makes the RPM more than twice that of 26" wheels that we have on our average bike.

 

[mountainsport]

There have been a number of postings on this topic and while not disagreeing with anything Woosh has said here is another take. An electric motor is just a conduit for converting electric energy into mechanical energy. The electric power going into the motor is the product of voltage and current. The mechanical power output is determined by the efficiency by which it can convert this into torque and rotational speed. Each motor will have been designed to have a speed at which this is optimised. If higher voltage is applied then either and both of more current flows increasing torque and depending on the technologies used, the motor rotates faster .
Typically a motor just consists of three sets of copper wire windings .. coils, the controller directs current to each set of windings in a sequence and this drags the rotor around. If excess current is used it will heat up the wire and the metal parts. Under some conditions the insulation around these windings can melt and the windings fuse together.
The mechanical parts respond to the torque produced and if this gets excessive internal gears get shredded..And bearings overheat. ..

Great that you have said that, therefore the signs of extreme levels of motor heating suggests that the systems volts or amps exceeds far beyond the capability of the motor thus causing a burn out.

 

[Woosh]

MS, there have been cases where the hall sensors are killed because the motor runs at too low speed for too long - eg on congested roads in London.
Direct drive motors are not good at low speed.

 

[mountainsport]

Far from it, they are some of the most beautifully designed and built pedelecs in existence. Their quality and that of their sister Koga pedelecs is outstanding.

Not very powerful and best suited to Dutch conditions at introduction, they now claim much higher torque though I think they somewhat exaggerate that.

For a rider in an undemanding area where no hill is over 10%, a good way to spend £2000. But my comments are restricted to the bikes with the Ion rear wheel DD hub motor. They make a few front hub motor bikes with a motor I know nothing about.
.

flecc, I hope that by saying this will not be added on to their private hate list, personally, I do not like a front wheel hub drive.

 

[mountainsport]

MS, there have been cases where the hall sensors are killed because the motor runs at too low speed for too long - eg on congested roads in London.
Direct drive motors are not good at low speed.

Tell me about it. I live in London and I have gone through 365 brake pads in just one year can you believe that? London is the worst and most dangerous place to ride including the bumpy and potholed roads.

 

[mountainsport]

When people burn out their motors and controllers, in most cases it's because they went too slow , which can be because they didn't give their motor enough power. Different motors are wound for different speeds. you can have 500w DD motors that climb like a goat with minimal power. Look at those electric scooters. They don't even have pedals to help them on the hills There's no exact answer to the question, You have to consider many things at the same time. Winding speed is fundamental, then there's torque. bike speed, output power, weight, incline, volts and current all affect it.

Never buy a motor unless you know it's winding speed. Once you know that, you can estimate everything else.

If you're thinking of a new bike, Mountainsport, tell us what you're trying to achieve. Maybe we can recommend something.

Thank you d8veh, I have always wanted to know from ever since and forgetting to ask this question because when I watch certain ebike videos people have said they have pushed their motors to the limit whilst still producing it to perform well during extreme added power.

 

[flecc]

flecc, I hope that by saying this will not be added on to their private hate list, personally, I do not like a front wheel hub drive.

Lots don't. I've owned front and rear hub motor bikes and a crank drive. I've liked them all for their differing qualities, but when reduced to one type only, it's rear hub motor for me.
.

 

[Danidl]

Great that you have said that, therefore the signs of extreme levels of motor heating suggests that the systems volts or amps exceeds far beyond the capability of the motor thus causing a burn out.

. Normally yes but the scenario produced by d8veh is also correct. If the voltage going into a motor is insufficient, it may not be rotating at its design speed . And is going slower. . this can also happen when the torque is insufficient for the load, this can , depending on the structure of the motor allow excess current to flow and burn out the windings. .. look up back EMF for details . A stalled motor usually will burn out.

 

[mountainsport]

. Normally yes but the scenario produced by d8veh is also correct. If the voltage going into a motor is insufficient, it may not be rotating at its design speed . And is going slower. . this can also happen when the torque is insufficient for the load, this can , depending on the structure of the motor allow excess current to flow and burn out the windings. .. look up back EMF for details . A stalled motor usually will burn out.

Ok then, in other words when a motor current flow is under or over the final outcome will be a damaged motor.

 

[flecc]

Ok then, in other words when a motor current flow is under or over the final outcome will be a damaged motor.

No, the damage will only ever result from the current being over the safe level, generating excess heat and resulting damage.

It's other factors being "under" that can bring about the excess current condition. Examples from Danidl's response:

Voltage insufficient turning motor slower than design speed.

Stalled motor which is also insufficient revs.

Torque insufficient for load.
.