【2026 Motor Issues】Ordinary motors cannot be used in high-altitude areas
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Why can’t ordinary motors be used in high-altitude areas? Elevation has an adverse effect on motor temperature rise, motor corona (in high-voltage motors), and the commutation of DC motors. The following three aspects should be noted: (1) At higher altitudes, the greater the temperature rise of the motor, the lower the output power. But when the temperature drops sufficiently with increasing altitude to compensate for the effect of altitude on temperature rise, the rated output power of the motor can remain unchanged ； (2) Corona prevention measures must be taken when high-voltage motors are used at high altitudes ； (3) Altitude is unfavorable for the commutation of DC motors; attention should be paid to the selection of brush materials.
The following motor knowledge is provided for reference: 1. When a single-phase transformer is operating without a load, the current is out of phase with the main magnetic flux; there is a phase angle difference of aFe due to the existence of iron loss current. The no-load current has a spike waveform due to the presence of significant third harmonics.
2. An alternating current also flows in the armature winding of a DC motor. However, direct current flows through its excitation winding. The excitation methods for DC motors include separately excited, shunt excited, series excited, and compound excited types.
3. The back EMF expression for a DC motor is E = CE·F·n； The electromagnetic torque expression is then Tem = CTFI.
4. The number of parallel branches in a DC motor is always in pairs. The number of parallel branches in the alternating current winding, on the other hand, is not necessarily fixed.
5. In DC motors, the elements of a single-stack winding are connected in series with one layer stacked on top of another. Whether it is a single-wave winding or a single-layer winding, the commutator connects all the components in series to form a single closed circuit.
6. An asynchronous motor, also known as an induction motor, is so named because the rotor current in it is generated through electromagnetic induction.
7、When an asynchronous motor is started with reduced voltage, the starting torque decreases, and it decreases in proportion to the square of the starting current in the windings.
8. When the amplitude and frequency of the primary side voltage remain constant, the degree of saturation of the transformer’s core remains essentially unchanged, as does the excitation reactance.
9. The short-circuit characteristic of a synchronous generator is a straight line; in the case of three-phase symmetrical short circuit, the magnetic circuit remains unsaturated； During a three-phase symmetric steady-state short circuit, the short-circuited circuit consists of a purely demagnetizing direct-axis component.
10. The current in the excitation winding of a synchronous motor is direct current, and the main excitation methods include excitation by an excitation generator, excitation by a static rectifier, and excitation by a rotating rectifier.