# 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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