Calculation of number of turns for armature banding

To calculate the number of turns of INTAF Polyglass Tape for any particular application.

Determine the tangential force F which the banding will have to withstand by using the formula:

         P x R x N²
F (kg) = ---------
         5.6 x 10⁶

where

P = weight of windings in kg exposed to the centrifugal force; normally is only end winding of the rotor/armature
R = maximum distance, in mm between windings and axis of rotation
N = number of revolutions per minute, at the maximum speed of rotation reached by motor

The number of turns of INTAF Polyglass Tape to be applied is obtained from the following:

    F x Ks
N = ------
    C x L

where

F = the force in kg determined above
Ks = the safety factor normally used (eg. Ks = 5)
C = tensile breaking stress of the tape, in kg/cm (180 kg/cm at operating temperature)
L = width, in cm. of the tape used for banding.

To compensate for some of the loss of tension it is normal to increase the calculated number of turns by a factor of 2 to 3.

Converting steel banding of Polyglass Tape

When replacing a steel band with banding tape, the required turn calculations are straight forward. First, determine the wire band strength by multiplying the number of turns by the ultimate tensile strength of the wire.

Wire band strength = Turns x Ultimate tensile strength

Now divide the wire band strength by the tensile strength of the selected banding tape material to determine the number of turns to use for an equivalent fiberglass band.

Wire Band Strength
------------------------------- = Turns (banding tape)
Tensile strength (banding tape)

TABLE 1: WIRED BAND STRENGTH
Size (AWG)	Ultimate Tensile Strength				Elastic Limit Strength
	Magnetic		Non-magnetic		Magnetic		Non-magnetic
	Lbs	Kg	lbs	Kg	lbs	Kg	lbs	Kg
14	774	351	738	335	503	228	443	201
15	615	279	585	265	400	181	321	146
16	486	220	462	210	316	143	277	126
17	378	176	368	167	251	114	21	100
18	306	139	291	132	199	90	174	79
19	243	210	231	105	158	72	138	63
20	193	88	183	83	125	57	110	50

The choice of glass banding tape should take into account the temperature and humidity of the application. High humidity banding material, for example, is manufactured using special moisture-resistant yarn. Other glass banding materials may be better suited for different environmental conditions or for higher or lower speed applications.

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