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I find these terms useful, so I’m reposting them. The original text reads as follows: If there’s anything wrong, please point it out! 1. Assigned power rating. Nominal power. or rated power. The ideal power during the design of the motor system is also the maximum power under recommended operating conditions. POWER RATING refers to the power. 2. Nominal voltage. Rated voltage. Or operating voltage, recommended voltage. Since ordinary motors can operate at different voltages, but the voltage is directly related to the speed, with other parameters changing accordingly, this voltage is merely a recommended value. Other parameters are also given at this recommended voltage. NOMINAL: Nominal in nature. 3. No-load speed. No-load speed, or idle speed. The unit is RPM. Revolutions per minute: Here, R does not stand for RATE, which refers to speed, but rather for REVOLUTION, meaning rotation. That is, how many revolutions per minute. I don’t know why we don’t use the number of revolutions per second; I’m unaware of this reference. I hope other netizens can provide it. Since there is no counteracting torque at no-load speed, the output power is different from that in the stall condition; this parameter merely indicates the maximum speed of the motor at a specified voltage. Generally, the 6,000 revolutions per minute or 12,000 revolutions per minute mentioned outside refer to this parameter. 4. Stall torque: Torque at stall. This is an important parameter for many motors that need to carry a load. That is, the torque when the motor is subjected to a reverse force that causes it to stop rotating. If motor stalling occurs frequently, it can damage the motor or burn out the drive chip; therefore, when choosing a motor, this is, I think, the first parameter to consider aside from speed. Its units come in a wide variety. There is mainly N.M, and there is also KG.M. The others are scales for these two units, such as CM, G, etc. As for conversion problems, I think there’s no need to talk about them anymore. Generally, its value is not closely related to the operating voltage, but rather to the operating current. Please note, however, that if the motor is in a locked-rotor condition for an extended period, its temperature rises rapidly, and this value will also drop significantly. 5. Speed/torque gradient: The slope of speed/torque. This parameter is rarely mentioned in general motor descriptions; after all, it’s MAXON, so it is present here as well. If the rotational speed is taken as the Y-axis and torque as the X-axis, generally, the motor starts with a line parallel to the X-axis, and then decreases in a manner similar to the negative exponential function of E. That is, the product of speed and torque, which decreases as torque increases. Motor manufacturers all recommend that motors operate within the range of that line parallel to the X-axis. Within this range, the current in the motor will not cause it to overheat or get damaged. 6. No-load current. No-load current. or no-load current. As mentioned earlier, current and torque are closely related. No-load current certainly exists, and the energy generated by the product of this current and voltage is primarily converted into potential energy and heat. Thermal energy refers to the heat generated in the motor coils; the better the motor, the lower this value is when it is running without a load. Potential energy, on the other hand, refers to the energy required to overcome friction, as well as the energy associated with the rotor’s own inertia and its rotational potential energy. When the rotational speed remains constant, the inertial energy of the rotor increases hardly at all. This potential energy is primarily used to overcome friction, and it is ultimately dissipated as heat energy. Therefore, the lower the no-load current, the better the performance of the motor. This is especially true for motors equipped with gearboxes; a lower no-load current indicates that the gearbox is of higher quality. Of course, the greater the gear ratio, the greater the resistance, under the same design conditions. 7. Starting current. Starting current. or initial current. This parameter is also quite important. The issue of rotor inertia mentioned earlier is even more evident here. A good motor has a lower starting current at the same acceleration, while poor motors are even worse – when used to drive a cart, they start moving slowly as if pulled by an ox, without any sense of speed typical of a racing car. MAXON’s motors have an advantage in this regard, as their rotors are well-designed. Hehe, I’m not his salesman, but his products are really good; Swiss goods are indeed excellent. The Germans are good too; in this regard, Japan and the United States still have something to learn from them. And this starting current needs to be taken into consideration in high-standard designs; otherwise, the drive chip might get damaged during startup. Moreover, this current is often several times greater than the maximum continuous current. For example, one model from MAXON has a maximum continuous current of 6A, while the starting current can reach 75A. It’s terrifying. 8. Terminal resistance, motor resistance. Hehe, I didn’t translate this very well. In MAXON’s Chinese manual, it is expressed this way: TERMINAL means terminal, and it can also refer to the resistance between the two output terminals of the motor. It’s actually the same. However, please do not think that this value divided by the rated voltage equals the no-load current. Because there is still electrical potential energy when the motor is rotating. There is also heat energy consumption. 9 Max permissible speed Maximum allowable rotation speed. This parameter generally has no effect. Since the rotation speed is controlled by voltage, this situation generally occurs in two cases. First, you’re not honest; you insist on using too high a voltage. Secondly, unfortunately, external energy drives the motor, resulting in such a rotation speed. And the general consequence of exceeding this speed is mechanical damage. However, this situation occurs very rarely. Ordinary motors don’t have such parameters either. 10. Max continuous current. Maximum continuous current. This current mainly refers to the current that occurs when there is a reverse external force, such as when a load is present. This is also a parameter that needs to be considered. Generally, the product of current and voltage is less than the rated power; it’s not that the motor has a certain loss ratio. However, operating under high current levels for extended periods, at or near the rated power, leads to an increase in temperature. The direct consequence of this is an increase in resistance, a decline in efficiency, and a reduction in overall performance, with the possibility of damaging the equipment as well. Operating at this value generally ensures normal operation for a long time. 11. Max continuous torque. Maximum continuous torque. It has a similar effect to that of the maximum continuous current. I won’t say anything more. This value is closely related to the maximum continuous current, but it is not exactly equal, as there is heat loss. 12. Maximum power output at normal voltage. Maximum output power at the rated voltage. It’s a bit strange; why is there such a parameter? I was puzzled by it too back then. Actually, there is a difference between this power and the rated power. This power level often does not take safety into account, and it is by no means a value that can be maintained for a long time; it is usually a measurement taken at a room temperature of 25 degrees Celsius. But this power is often higher than the rated power; from the information I’ve seen, for example, a model from MAXON has a rated power of 150W, while in another model this value is 491W. Pretty terrifying, right? And it’s not very useful either. Don’t expect your motor to be able to work under the influence of stimulants every time. Viagra is actually very harmful to the body; I’ve never taken it, but one can make an analogy from this. 13. Maximum efficiency. Maximum efficiency. It is generally measured at room temperature. Voltage multiplied by current, with efficiency taken into account, generally gives the output power. However, if the motor runs for a long time, this efficiency will decrease slightly; of course, not by much, unless your motor is already capable of roasting sweet potatoes. This parameter is generally used to calculate the relationship between several values, such as the relationships between voltage, current, and rotational speed or torque. 14. Torque constant. Constant of torque. It does not refer to static torque here. The units are N.M/A, etc. That is, the torque value per A, or per milliampere; this is also an auxiliary parameter with limited practical use. However, when choosing a motor, this value is another factor that can be taken into consideration. But in fact, in actual measurements, this value is not a constant. 15. Speed constant. The rate constant, namely RPM/V, indicates by how much the speed increases for each increase of 1V. In fact, just like above, the range within which it remains constant is also limited; don’t expect that applying 100 times more voltage will result in 100 times higher speed. Generally, the higher the voltage, the lower this value becomes. 16. Mechanical time constant. Mechanical time constant. If I remember correctly, this parameter is the time it takes to reach 63% of the normal operating speed (this is MAXON’s standard; I’m not sure what the standards are for other companies). (I’m hungry and want to eat, so I don’t have time to look up reference materials.) MAXON values are usually in the range of a few MS; actually, this parameter also provides us with information regarding how to control the starting and stopping of the motor. If it’s less than 1 MS, it actually doesn’t make much sense; the motor itself has inertia, so there isn’t enough time for it to stop rotating, and that naturally leads to control problems. 17. Rotor inertia: the inertia of the rotor. As mentioned earlier, regarding acceleration and deceleration, in the case of no load, the lower this value, the better. However, if the load itself has a high inertia and this value is already relatively high, then it makes little sense to spend money on reducing it. 18. Terminal inductance: Motor inductance. Well, the tragic story I want to share is that I had to take a make-up exam in electromagnetic fields during my undergraduate studies; so please let those who are experts in this area explain it to me – I’ll step back for now. 19 Thermal resistance housing –ambient: The thermal impedance from the motor enclosure to the environment. This value is actually quite interesting to look at. But generally, motors don’t have them. Since this value represents the heat generation per watt of power when there is no cooling, the lower it is, the better. 20. Thermal resistance rotor-housing: The thermal impedance from the rotor to the housing. Basically the same as above. Small is better than large. 21. The thermal time constant of a winding is the time it takes for the temperature of the winding to change. It is a unit of degrees per second. This thing is actually pretty impressive. It seems we won’t need it yet.