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I'm currently planning to run a DC motor continuously on solar power. So I would like to know which things I should be very careful about for optimum lifespan of the motor. I found the following two, and would like to know what other factors do:

  1. Voltage
  2. Current Source
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Voltage and current - Basically because you will run your motor continuously, you will want to run your motor at or below its nameplate rating. Too high of a current means your motor will heat up too much (see below). Higher current also increase the current density in your brushes which will shorten life. Too high of voltage would mean your motor is rotating faster than typical and could reduce bearing life. At higher speeds your brush pressure may not be optimized, either, so you could reduce brush life.

Temperature - Most standard motors are designed for a maximum ambient operating temperature of 40 °C. This temperature takes into account the temperature rise that will result from running your motor at its rated temperature. If your ambient temperature goes above 40 °C (or if you run your motor above its nameplate rating) your motor may getting hotter than it should. If the motor gets too hot, it may affect the life of the insulation, the life of the bearings, or the life of the brushes. If insulation temp is an issue, you can go to a higher class insulation (for example, from Class B to Class F or from Class F to Class H). If bearing temp is an issue, you can look at getting higher temperature grease in your bearings. The temp of your brushes can cause a change in the friction between brush and commutator. You can get different grade brushes with different coefficients of friction that can help you with this. Low temperatures can also affect life. For example, your bearing grease has a lower temp limit as well and you can specify a low temp grease if necessary.

Moisture - If your motor is outdoors or needs to be washed down, then your motor should be sealed. Basically you want to prevent corrosion on metal parts. You can get sealed bearings, water-proof wire exits, o-rings between end bells and housings, etc. to prevent leaking. High humidity can actually cause brushes to have a shorter life, too.

UV - Some plastics and rubbers will degrade in sunlight, so if the motor will see direct exposure to UV, you will want to make sure your materials are compatible. This may affect lead wires, grommets, brush holders, etc.

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Good bearings and brushes, preferably self lubricating

voltage equates to speed of rotation - more volts, faster rotation

current equates to torque. More load, bigger current.

Explanation

Basically the speed at which the motor turns induces a back e.m.f. just under the value of the applied voltage. The actual speed depends upon the type of motor but for small DC motors a rough guide is about 1000 r.p.m. per volt

The current that flows through the motor is determined by the difference in these two voltages and the coil resistance.

Adding a load on the motor's shaft (torque) slows it down and increases the voltage drop across the windings as the back e.m.f. is reduced. This increases the current taken by the motor.

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This is a very broad subject, only partly touching on electrical engineering. I suggest finding a good mechanical engineering source on motor installations. First thing that popped up when I searched for a definition of 'axial load' was the Bodine manual.

Offhand, the first thing that will wear out a motor is asking its bearings to support loads they are not designed for. Avoid side to side forces on the shaft, and axial forces: enter image description here

The next thing that will wear out a motor is over-temperature. Provide cooling if it needs it. At the very least, do not obstruct it's cooling vents!

Bearing seals can fail, lubricants can run dry. Brushes wear out, grit can get in the gears. So keep it clean and protected, and at the same time available for inspection.

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Avoid starting and stopping. That definitely hurts motor life. That's why your AC won't turn and off quickly when you switch it on and off quickly. There is a minimum time in the controller to avoid that.

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    \$\begingroup\$ Starting and stopping, on its own, isn't necessarily bad. Starting under load is the issue. When you stop the AC (air conditioner), there is pressure in the compressor system. If you try to start up again immediately the motor has to work against that pressure. There is usually some kind of bleed off system that reduces the pressure over time. There is either a time delay, or a pressure sensor that prevents the stystem from attempting to restart right away. The same applies to refrigeration systems and air compressors. \$\endgroup\$ – jwygralak67 May 21 '13 at 18:41

protected by W5VO May 21 '13 at 18:36

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