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Dc Motor
1.Torque Conversion Chart
























































2.Precautions for Handling Geared Motors
Precautions for Handling Geared Motors

Turning by output shaft

Do not turn a geared motor by its output shaft when, for example, arranging its position so as to install it. 
The gearhead will become a speed-increasing mechanism, which will have harmful effects, damaging the gears and other internal parts; and the motor will turn into an electrical generator.

Installed position

For the installed position we recommend a horizontal position --the position used in our company's shipping inspection.
With other positions, grease might leak onto the geared motor, the load might change, and the motor's properties might change from those in the horizontal position. Please be careful.

Additional processing

Various kinds of processing are possible for the output shaft.
¡ùHowever, it is necessary to be careful when processing, as the load,an impact, powder from cutting, etc., during processing can damage the product.


Install the screws after first checking the taps and tap depth against the dimensions entered on the exterior drawing.
¡ùIf, when a geared motor is installed, the screws are too long or their tightening torque is too great, the motor's internal mechanical parts could become deformed or break or the screws could become deformed, resulting in a breakdown. If the tightening torque is too weak, on the other hand, it could cause the motor to rattle or fall off.

Installation of geared motor on output shaft

Please be careful with regard to applying adhesive.
¡ùIt is necessary to be careful that the adhesive does not spread along the shaft and flow into the bearing, etc. Moreover, do not use a silicon adhesive or other volatile adhesive, as it could harmfully affect themotor's interior. In addition, avoid press fitting, as it could deform or damage the motor's internal mechanism.

Handling the motor terminal

Please conduct the welding work in a short time.. (Recommendation: With the soldering iron tip at a temperatureof 340 - 400¡æ, within 2 seconds.)
¡ùApplying more heat than is necessary to the terminal can melt the motor's parts or otherwise harm its internal structure. Moreover, applying excessive force to the terminal area can put stress on themotor's interior and damage it.


Grease is applied to the sliding areas of the gears, etc.
¡ùBe careful about using the product in a special environment. Due to the structure of geared motors, the grease could ooze out to the exterior.

Temperature range for use

Geared motors should be used at a temperature of -10¡«60¡æ. The figures stated in the catalog specifications are based on use atordinary room temperature (approximately 20¡«25¡æ.
¡ùIf a geared motor is used outside the prescribed temperature range,the grease on the gearhead area will become unable to functionnormally and the motor will become unable to start. Depending on the temperature conditions, it may be possible to deal with them by changing the grease or the motor's parts. Please feel free to consult with us about this.

emperature range for storage

Geared motors should be stored at a temperature of -15¡«65¡æ.
¡ùIn case of storage outside this range, the grease on the gearhead area will become unable to function normally and the motor will becomeunable to start.

Relative humidity range

Geared motors should be used in 20 - 85% relative humidity (no dew condensation).
¡ùIn a humid environment, the metal parts might rust, causing abnormalities. 
Therefore, please be careful about use in such an environment.

Long-term storage

Do not store a geared motor in an environment where there are materials that can generate corrosive gas, toxic gas, etc., or where the temperature is excessively high or low or there is much humidity. Please be especially careful with regard to storage for lengthy periods such as 2 years or more.


The longevity of geared motors is greatly affected by the load conditions, the mode of operation, the environment of use, etc. Therefore, it is necessary to check the conditions under which the product will actually be used. The following conditions will have a negative effect on longevity. 
Please consult with us should any of them apply. 
¡öUse with a load that exceeds the rated torque   ¡öFrequent starting 
¡öMomentary reversals of turning direction            ¡öImpact loads 
¡öLong-term continuous operation    ¡öForced turning using the output shaft   
¡öUse in which the permitted overhang load or the permitted thrust load is exceeded . 
¡öA pulse drive, e.g., a short break, counter electromotive force, PWM Control 
¡öUse of a voltage that is nonstandard as regards the rated voltage
¡öUse outside the prescribed temperature or relative-humidity range, or in a special environment
¡öPlease consult with us about these or any other conditions of use that may apply, so that we can be sure that you select the most appropriate model.

3.Why choose a D.C motor? 
        Many applications call for a high start-up torque. The D.C. motor, by it svery nature, has a high torque vs. falling speed characteristic and this enables it to deal with high starting torques and to absorb sudden rises in load easily. The speed of the motor adjusts to the load. Furthermore, the D.C. motor is an ideal way of achieving the miniaturisation designers are constantly seeking because the efficiency it gives is high compared with other designs.

4.How to select from the LEISON MOTOR range? 
         The motor unit is selected according to the required output power.Depending on the required speed, a direct motor or a geared motor is selcted.
Speeds 1,000 to 5,000 rpm¡¡¡¡¡¡¡¡¡¡¡¡Direct motor
Speeds below 500 rpm ¡¡¡¡¡¡¡¡¡¡¡¡¡¡Geared motor
The gearbox is selected depending on the maximum required torque and the duty cycle


5.Definition of the DC motor 
        This motor follows linear laws of operation and because of this it is easier to fully exploit its characteristics compared to synchronous or asynchronous motors.
1)Composition of a D.C. Motor£ºThe stator is formed by a metal carcass and one or more magnets that create a permanent magnetic field inside the stator. At the rear 
of the stator are the brush mountings and the brush gear which provide electrical contact with the rotor.The rotor is itself formed by a metal carcass carrying coils which are interconnected at the commutator at the rear of the rotor.
The commutator and brush assembly then select the coil through which the electric current passes in the opposite direction.
Principle of operationWhatever the complexity of the rotor coil windings, once they areenergised, they may be represented in the form of a ferromagneticcylinder with a solenoid wrapped around it.
The wire of the solenoid is in practice the wire bundle located ineach groove of the rotor. The rotor, when energised, then acts as anelectromagnet, the magnetic field following the axis separating the wiresof the solenoid in the direction of the current which flows through them.
 (DRW 1)   (DRW 2)
The motor, therefore, consists of fixed permanent magnets (the stator) amoving magnet (the rotor) and a metal carcass to concentrate the flux(the motor body).(DRW 1)
(DRW 2)By the attraction of opposite poles and repulsion of like poles, a torque then acts on the rotor and makes it turn. This torque is at a maximum when the axis between the poles of the rotor is perpendicular to the axis of the poles of the stator.As soon the rotor begins to turn, the fixed brushes make and break contact with the rotating commutator segments in turn.The rotor coils are then energised and de-energised in such a way that as the rotor turns, the axis of a new pole of the rotor is always perpendicular to that of the stator. Because of the way the commutator is arranged, the rotor is in constant motion, no matter what its position. Fluctuation of the resultant torque is reduced by increasing the number of commutator segments, thereby giving smoother rotation.By reversing the power supply to the motor, the current in the rotor coils,and therefore the north and south poles, is reversed. The torque which acts on the rotor is thus reversed and the motor changes its direction of
rotation. By its very nature, the D.C. motor is a motor with a reversible direction of rotation.
Torque and speed of rotation
The torque generated by the motor, and its speed of rotation, are dependent on each other.
This is a basic characteristic of the motor ; it is a linear relationship and is used to calculate the no-load speed and the start-up torque of the motor.(DRW 1)
 (DRW 1)        (DRW 2) 
The curve for the output power of the motor is deduced from the graph of torque versus speed. (DRW 2)The torque vs. speed and output power curves depend on the supply voltage to the motor.
The supply voltage to the motor assumes continuous running of the motor at an ambient temperature of 20¡æ in nominal operational conditions.
It is possible to supply the motor with a different voltage (normally between -50% and + 100% of the recommended supply voltage).If a lower voltage is used compared to the recommended supply the motor will be less powerful.If a higher voltage is used, the motor will have a higher output power but will run hotter (intermittent operation is recommended). 
For variations in supply voltage between approximately - 25% to + 50%,the new torque vs. speed graph will remain parallel to the previous one.Its start-up torque and no-load speed will vary by the same percentage (n%) as the variation in supply voltage. The maximum output power is multiplied by (1 +¦Ç%)2. 
Example : For a 20% increase in supply voltage
Start-up torque increases by 20% ( x 1.2)
No-load speed increases by 20% ( x 1.2)
Output power increases by 44% ( x 1.44)
Torque and supply current
This is the second important characteristic of a D.C. motor.It is linear and is used to calculate the no-load current and the currentwith the rotor stationary (start-up current).
 The graph for this relationship does not vary with the supply voltage
of the motor. The end of the curve is extended in accordance with the torque and the start-up current    .
This torque constant is such that:£ºC=Kc(I£­Io)   The otational friction torque is Kc. Io.    The torque is therefore expressed as follows :C=Kc. I£­Cf   Cf=Kc. Io
Kc = Torque constantr (N.m/A)           C = Torque (N.m)
Cd= Start-up Torque (N.m)                 Cf = Rotational friction torque (N.m)
I = Current (A)                Io = No-load current (A)               Id = Start-up current (A) 
The gradient of this curve is called the ¡°torque constant¡± of the motor.
The efficiency of a motor is equal to the mechanical output power that it can deliver, divided by the power which it absorbs.The output power and the absorbed power vary in relation to the speed of rotation, therefore the efficiency is also a function of thespeed of the motor.Maximum efficiency is obtained with a given rotational speed greater than 50% of no-load speed.
Temperature rise
The temperature rise of a motor is due to the difference between the absorbed power and the output power of the motor. This difference is the power loss.Temperature rise is also related to the fact that power loss, in the form of heat from the motor, is not rapidly absorbed by the ambient air (thermal resistance). The thermal resistance of the motor can be greatly reduced by ventilation.
The nominal operating characteristics correspond to the voltagetorque-speed characteristics required for continuous operation at an ambient temperature of 20¡æ. Only intermittent duty is possible outside these operating conditions : without exception, all checks concerning extreme operating conditions must be performed in the actual customer application conditionsin order to ensure safe operation.
6.Motor and gearbox combinations 
D.C. motors are constructed to operate continuously within a range of speeds near their no-load speed. This range of speeds is generally too high for most applications. In order to reduce this speed, a full range of geared motors is available, each with a series of gear ratios to suit most speed requirements.The complete range is suitable for a wide variety of applications.
Gearbox characteristics£º
Our gearboxes have been designed for optimum performance and for maximum life under normal operating conditions.Their main characteristic is the capacity to withstand maximum design torque with continuous duty.The range of gearboxes shown in this catalogue can operate with maximum torque of 0.5 to 6 N.m for long time periods. All values previously stated are for standard products in normal operating conditions, as specified.In certain cases, these values may be increased if a shorter life is required.Please consult our Sales Office for further information.Every gearbox has a torque limit, which is the breaking torque If this torque is applied to the gearbox, it will cause severe damage.
Gearbox construction  
The module,depth and material of Gears are calculated according to the stress of gear at each step. By life test of motor to produce the motor with low noise and enough life time. Gearbox can be assembled with DC motors, DC brushless motors and shade pole motors.
Selection of a geared motor£ºA geared motor is selected according to the required usable power output.
useableP(W)=           useableP(W)=
useableP(W)=               useableP(W)=
Selecting the reduction gear ratio£ºTwo selection criteria may be applied.
* The first criterion concerns the required speed output of the reduction gear only. It is adequate for most applications and is easy to apply. Given that :
             N1= required speed of geared motor             B1=basic nominal speed of motor
* The second criterion concerns the required usable power output of the motor. The rotational speed of the motor is given by :
N = speed of motor(rpm)                  No = no loadspeed of motor(rpm)         
P = required output power(W)         Cd = start-up torque of motor(Nm)
this gives the equation:                                                 
 In order to avoid using numbers less than 1 where the reduction ratio is concerned, the value 1/R is employed.
Due to the fact that it is always a reduction gear and not a "ultiplier" gear, there should be no ambiguity concerning the number used.
7.Product technology introduction 
1)£®1.Generally reducer with single pair of gears transmission, parallel shaft structure and ordinary gear train is called gear reducer. Mostly straight gear and slanting gear are used in mini gear reducers. The reduction ratio of mini gear reducer is generally designed within range 1:200 except of extremely mini reducers.
2.)Planetary gear reducer is a transmission structure of multi pairs of gears Transmission and dynamic gear train, spanning wide range of reduction ratio up to max. reduction ratio 1:1730. The planetary gear reducer has the character of small figure, light weight, heavy load, high efficiency and stable running. Compared with gear reducer, it can save 30%---50% both of volume and weight, specially suitable fro application requesting big reduction ratio and compact structure. Now for the reason that the speed of DC motor is hardly up to 1000 per minute but DC motor of relatively light rotating speed can lower speed and enhance torque after being assembled together with planetary gear reducer of small reduction ratio, Planetary gear reducer is frequently equipped in application requesting high rotating speed.
3.)The main character of worm reducer is of crossed-axis transmission. 90 degree angle between output shafts of motor and reducer, stable running,low noise and self locking function. Its shortage is low efficiency. 
4.)Rated load torque: output torque of motor at status of rated voltage, rated frequency and rated speed (of the diagram). The general calculation formular:Rated load torque=rated torque of motor X reduction ratio X transmission efficiency of reducer,Restrained by the maximum torque of reducer of big reduction motor,the maximum torque value is equivalent to the rated one. if the calculated value of rated load torque is bigger than the maximum torque.
5)Transmission efficiency of reducer: Torque efficiency of motor equipped with reducer, usually expressed in percentage. It is influenced by friction of bearing and gear, and condition of lubricating grease. Generally the transmission efficiency is 90%, transmission is 95% after the first gear train, and 81% after the second gear train. Bigger reduction ration requires motor gear trains and leads to lower transmission efficiency.The transmission efficiency of planetary gear reducer is much higher, generally its efficiency of one gear train.
8.Torque Caculation method of induction geared motors.
Torque Caculation method of speed control motor and geared motors£º 
1. Motor without gearbox, after adjust speed, output torque is "Mn",output speed is "n", motor speed at 1300 rpm, torque is "M1300",when the motor turn 90 degree, output toque is "M90",the formula is Mn=(M1300-M90)/1200X(n-90)+M90.
.2. Motor after geared reduction, the torque is "Mi", ratio is "i" ,the running efficiency is "¦Ç",the formula Mn X i X ¦Ç 
Note: running efficiency 
a¡¢reduction ratio 1:4-1:18£¬ ¦Ç ¡Ö81% 
b¡¢reduction ratio 1:25-1:36£¬¦Ç ¡Ö73% 
c¡¢reduction ratio above 1:50£¬¦Ç ¡Ö66%

If the motor is used beyond the above conditions,please inform us.


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