How to select coreless dc motor?

   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:

1.Power matching

   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.

(1)Determine basic application data:

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)

(2)Calculate output efficiency of motor required:

Output efficiency:
		(W)
	(W)refers to efficiency of operating point

(3)After(1)(2)is determined,consult production catalogue to select appropriate motor.

2.Motor operating mode and environmental conditions

   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.

3.Motor Operating Life

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.

4.Operation Efficiency

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:
is no load current;	is operating current.
Our experience has shown thatmax 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 .

   Coreless motor is a precision DC, PM, servo motor whose inner structure is completely different from conventional ironed DC, servo motor. So assembly method of ironed DC servo motor is not appropriate to coreless motor.
   In order to avoid damage during installation, particular explanations as follows:
   Assembly with Motor:
   We suggest two kinds of assembly method:
   Front flange assembly and stop table positioning:
   We recommend this type of assembly method if possible. Use stop table to orient and use the screw hole of assembly end to connect.
   The recommended tolerance for the part fitting stop table is H8;
   The maximum entering depth of assembly screw can not exceed effective depth of screw as shown in product manual, otherwise it might cause damage to inner structure of motor or impact operation performance.
   Housing positioning and assembly:
   When front flange assembly and stop table orientation can not be used, such as a gas analyzer, we can employ two pieces of semicircle board to press housing of motor and fix.
   The recommended tolerance for the part fitting motor housing is H8;
   To avoid partial deformation caused by incorrect assembly method, such as using flat press board or screw.
   Assembly and Connection with Motor Output Shaft:
   When gearbox or strap wheel etc on output shaft of motor needs to be assembled, the f sticking, hot assembly or screw assembly could be chosen.
   Use oxygen-free glue when sticking, the tolerance of the part fitting output shaft of motor is recommended at H8;
   No cold press assembly to be applied when fixing parts on output shaft of motor.
   Maximum permissive load on output shaft of motor:
   Maximum permissive load output shaft of motor is limited; the motor will cause damage if exceeding the maximum permissive load. For details, see product manual.
   Please select ball bearing when the motor endures radial loads and sleeve bearing when even load.
   Soldering condition of motor terminals:
   Please notice the following requirements when soldering leads on the terminals of motor.
(1) Soldering temperature:215

(or the max. power of electric iron is less than 40W);
(2) Soldering time(refers to contacting time between electric iron and terminals)is less than 3 seconds;
(3) Electric iron can not touch the plastic back cover of motor;
When soldering leads, if the plastic back cover is melt, the motor may be damaged.
If you have any questions, please contact our sales department.

ADD:No.9,Shuangyuan Road,Badachu Hi-Tech Park,Shijingshan District,Beijing. P.C:100041

Tel:(086)10-88795742 Fax:(086)10-88798682 E-mail:sales@e-ds.cn