What kind of motor is best?

What kind of motor is the best? Which one is better, a certain motor or another? Should I use motor A or motor B? Which motor is more energy-efficient?

This is a most common question. The production of motors includes several physical parts: magnet, iron core, coil, base, Hall, insulating paint, and phase line. Let's analyze them one by one below.

There are five indicators for magnets: number, height, thickness, width and quantity. The number represents the magnetic flux per unit volume, which is the level of the magnet. It cannot be seen with the naked eye and can only be fooled by the manufacturer. The height, thickness, width and quantity are, of course, higher, thicker, wider and more. The larger the volume of the magnet, the higher the cost for the motor manufacturer, and the greater the power for the user, which of course also means that the power consumption will be higher.

Based on the principle that the higher the manufacturer's cost, the greater the user's benefit, and on the premise of meeting one's own requirements for power, the higher the height*thickness*width*number, the better. However, generally speaking, for users, the thickness, width and number are uncertain. Everyone only knows that the motor is 30 high, 40 high or 45 high.

Of course, imported iron cores are better. The moon in foreign countries is rounder than the moon in China, but it cannot be seen with the naked eye. This is all we can assume for now.

The coil, copper purity (brass or red copper, as long as it is not copper-clad aluminum), number of turns, thickness, and full slot rate are the main parameters.

Once the base is determined, the upper limit of space indicators involving quantity and volume will be determined. However, we users still have no choice, and the same goes for manufacturers.

Hall, an electronic component, is something that can only be distinguished by money. Currently, the Honeywell brand on the market is better.

The country has given five grades to insulating paint, and the higher the temperature resistance, the better.

The thicker the phase wire is, the better. Generally, 1 square meter (excluding rubber) can meet the 10A current limiting requirement. For example, if your current limiting control is 20A, the phase wire must be more than 2 square meters.

Power - a point in the motor index. For example, your original motor is 48V 500W, and the speed is 36 km/h. Then you overvoltage it to 72V, and you will find that the speed can reach 54 km/h. Divide the motor speed by the voltage, and the result is more accurate. For example, if your current speed is 45 km/h, if your voltage is 72V, then your motor speed per volt voltage is 0.625. Another motor speed is 40 km/h, but the voltage is 48V. The speed of this voltage per volt voltage is 0.83333. You can tell which one is faster by comparing.

Efficiency (power saving)----Electric vehicle motors are just like that. The motors we are using generally have an efficiency of around 82%. If they are regular products, the difference is only around 2%. You say your motor is very good and uses the most advanced technologies such as high-temperature superconducting technology, so the difference can only be increased by 3 percentage points at most. However, the difference should not be too obvious.

This is why many people have reported that a certain motor (power-saving version) does not save obvious power. Of course, some people say that they really do save power, but they are either really cheating or the original motor is just rubbish.

But everyone will also feel that some motors are indeed more power-consuming. This is easy to understand. It is difficult to increase the efficiency by 1%, but there is a lot of room for improvement. It is still easy to make a motor with an efficiency of only 50%.

Best efficiency point - the key to overpressure

As we said above, efficiency is an indicator with a wide range of potential but a nearly fixed upper limit. So is it completely unnecessary to consider the motor efficiency indicator? The answer will not surprise you.

We should pay more attention to another important indicator——the best efficiency point

The so-called best efficiency point refers to the point of best efficiency. For example, a manufacturer says that the best efficiency of its motor is 93%. You ask him, "When does this 93% efficiency appear?" If he says, "When the motor is 48V and the power is about 100W," you will faint, because you will not maintain a power of 100W, that is too slow. Of course, if the manufacturer wants to fool you, he will definitely not tell the truth, or he simply does not know.

In the motor industry, the best efficiency point refers to the power at the best efficiency point within the rated voltage and rated power range. For example, a 48V1000W motor is powered on at 48V for dynamometer testing. When the dynamometer chart comes out, you look at the lines around 1000W. If you see a highest efficiency value of 82.5%, and the corresponding power is 960W, but the corresponding efficiency value at the 1000W power point is only 81%, this means that the best efficiency point of this motor is 960W.

Of course, for regular factories, the best efficiency point is around the rated power point, with a difference of less than 5%. But this is not necessarily the case for some factories. The highest efficiency value is 83%, which is good, but this 83% is at the 48V500W power point. He said that this motor is 72V1500W. We bought it and used it at 72V, and the efficiency at 1500W is only 65%.

What I have said above is just to explain that this is the case. Later we will have a simple method to know what our motor is like.

First of all, you need to determine your usage requirements. This is definitely not the case that the faster the better. If you want a motor that can reach 100 km/h at 72V, then you don’t need to consider the quality of the motor, because safety and quality cannot be guaranteed.
In terms of normal use, when the speed exceeds 50 yards, it has entered the unsafe zone.

Here is a simple power-speed comparison table for you:

Power Speed ​​(yards)
350W 35 500W 40
800W 45 1000W 50
1200W 53 1500W 55
2000W 60 3000W 65
4000W 75 5500W 85
7000W 90 8500W 95

10000W 100 12000W 110
15000W 120

Therefore, when ordering a motor, consider its scope of use, especially if you plan to overpressure it, don’t make it too large.

Let's summarize it below and give you something simple and practical. As mentioned above, you can't just look at the power. When buying a motor, how should you choose the motor?

First of all, you need to determine your speed requirements, voltage and force requirements. If you plan to over-pressurize in the future, it is best to determine the fastest speed you hope to achieve after over-pressurization.

Then, divide the required speed by the voltage used. For example, if you plan to buy a motor with an overvoltage of 72V and hope that the maximum speed is greater than 75 km/h, then 75/72=1.0416.
Then you need to find a motor with a speed divided by the voltage that is just greater than 1.0416 to meet your requirements. Note that it must be just greater than that. If it is much larger, it will consume more electricity.

A motor 48V500W speed 36; B motor 48V800W speed 42; C motor 60V1200W speed 45; D motor 60V1500W speed 52; E motor 48V1000W speed 45, F motor 48V1500W speed 52

After some calculation, only the F motor is suitable among these motors.

Therefore, it is meaningless to just say how many volts the motor is used for, it is meaningless to just say the speed, and it is meaningless to just say the power. If you can order a motor, you must first say the motor size and magnet height, because this determines the physical space inside the motor, and this space must be maximized to allow the motor factory to have the maximum possible use of materials. This is what I mean by motor size (all for ordering electric motors) and magnet height. Of course, the higher the magnet, the more expensive it is, and this is a question of your own trade-off.

The next step is to set the maximum voltage and maximum speed indicators, telling the motor manufacturer how much voltage you want to exceed and how much speed you want to achieve. Then, the speed is determined. Once the base is determined, the slower the motor, the higher the cost.

At this time, you can ask that the speed should not exceed 42 at 48V, otherwise you will have to return the product. Because the base is fixed, if you want to reduce the speed, you can only increase the number of coil turns, increase the full slot rate, use a good iron core, etc. Otherwise, the speed cannot be reduced. You don't have to worry about the high power consumption of the magnetic steel, because the current parameters are determined by the controller.