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 How to select coreless dc motor? |
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Due to obvious differences in performance and price betweenDC coreless motor and ironed rotor motor,product designer and electrical engineer should have a concern about how to select a particular motor to make use of the advantage of coreless motor and meet requirements.
We suggest that the motor should be operated at the most efficient area when customer selects high-quality coreless motor,so it is essential to confirm working range and condition together.
The five factors below should be considered: |
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Power matching is mainly involved in operating voltage,operating current,operating speed and operating torque.
In general, operating voltage and operating speed is easy to choose according to requirements, while operating torque is often defined by particular testing equipment or experimental data. Operating current is concerned with operating torque, we can get operating current due to particular torque according to related formula.
Take the efficiency of gearbox causing energy loss into account when assembling it.
Technical data abroad often refers to max. power of motor not normal operating output power, so please consider its difference carefully when selecting motor. |
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| (1)Determine basic application data: |
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| Torque required M |
(mN.m) |
Speed required n |
(rpm) |
Max. Voltage U |
(V) |
| Max. Current I |
(A) |
Max. Permissible Dia. Of motor |
(mm) |
Output shaft load: Axial/radial |
(N) |
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| (2)Calculate output efficiency of motor required: |
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| Output efficiency: |
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(W) |
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 (W) refers to efficiency of operating point |
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| (3)After(1)(2)is determined,consult production catalogue to select appropriate motor. |
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| 2.Motor operating mode and environmental conditions |
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The motor usually includes several modes of operation such as constant load continuous run, variational load continuous run, intermittent run, impactive load run, forward and reverse run or a combination of condition above. There is a little difference considering actual mode of application when selecting motor.
Some application requires motor to produce disturbing signals as little as possible. How to make the speed of motor and load fit decides magnitude of disturbing.
Operating condition has a close relation with the choice of motor. For example, the magnitude of operating current is directly proportion to operating life when supplying power with batteries. Ambient temperature is a important factor in affecting output parameter of motor, and also impaction and vibration have an effect on operating status of motor. |
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Operating life is related with manufacture precision, quality and dimension of commutator. However, operating mode of motor, load (operating current), operating speed and environment condition also influence life. From our experiment, we learn that continuous operating life will exceed ten thousand hours under lower current and speed while only have several hundreds of hours under high-limited.
There is a marked difference of life due to distinct operating mode and environment condition. 1000-3000 hours data sheet mentioned refers to life at unilateral constant load within the period of operating area. |
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| We suggest that the motor should be operated within fifteen percent of the max. efficiency point in order to take use of high efficiency of coreless motor and keep high motor life. We consider internal structure of motor as well as efficiency when recommending the upper limit of operation. Product introduction of coreless motor abroad often marks very high continuous operating current which affects lifetime in the product explanation. |
| Max.efficiency: |
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 is no load current; |
 is operating current. |
Our experience has shown that max is close to U/7R=IB, so the range of IB should vary from U/7R to the upper limit of continuous operation. |
| 5.Dimension Of Motor And Assembly |
Coreless motor is one of the most efficiency of energy exchange. Customers usually pursues smaller dimension, and we can provide five types of model from diameter 16mm X 25mm to 36mm X 72mm, ten kinds of dimension and dozens of spec. for a choice, however, a particular dimension of motor or planetary gearbox can be done owing to user's requirements.
Assembly dimension of gearbox mainly depends on relative parameter of output shaft and hole of bolt. |
| Notes: |
1.Please look technical data and attention through in the product sheet in order to avoid damage in use or assembling.
2.Please compare terms explanation and relative formula not merely depending on technical data for a choice due to different point of expression every manufacturer.
3.Please contact manufacturer when user can not supply necessary data of selecting motor or have other requests .
4.Please contact manufacturer when user can not supply necessary data of selecting motor or have other requests . |
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