THE ORIGINAL MAGNETIC PARTICLE SPECIALISTS

Magnebrake® Engineering Calculations

See Below for Magnebrake® Engineering Calculations on the following applications:

Magnetic Particle Brake on a Non-Contact Unwind
Magnetic Particle Brake for Controlled Deceleration
Selection - Heat Dissipation (Slip Watts) vs. Speed Chart (RPM)


Magnetic Particle Brake on a Non-Contact Unwind

engcalc1.gif

Web Force (F)Web Speed (V)Core Diameter (d)Full Roll Diameter (D)
125 lbs. 200 fpm 3 in. 30 in.
1. Calculate Torque

T = F x r
T Start = 12 lbs. x 30/24 ft. = 15 lb.-ft.
T Finish = 12 lbs. x 3/24 ft. = 1.5 lb.-ft.

2. Calculation Speed

N = V/πd
N Start = 200 / π x 30/12ft. = 25 rpm.
N Finish = 200 fpm / π x 3/12 ft. = 255 rpm.

3. Calculate Slipwatts

SW = T x N Slip / 7.04
SW Start = 15 lb.-ft. x 25 rpm / 7.04 = 53 Watts
SW Finish = 1.5 lb.-ft. x 255 rpm / 7.04 = 53 Watts

4. From Slipwatts vs rpm curves

The 25MB90S will dissipate 140 Watts at 255 rpm.

5. Select 25MB90S.



Magnetic Particle Brake for Controlled Deceleration

engcalc2.gif

Inertia of Load (WK2)Speed of Load (N)Time to Stop (t)
1000 lb.-ft.2 360 rpm 60 sec.
1. CalculateRequired Torque

T = WK2 (rpm) / 308t
T = 1000 lb. - ft.2 (360 rpm) / 308 x 60 = 19.5 lb. - ft.

2. Calculation Speed

SW Max = T x N Max / 7.04
SW Max = 19.5 lb. - ft. x (360 rpm) / 7.04
SW Max = 966 Watts

3. Calculate Slipwatts

SW avg = √( t on / t on = t off x 1/3 x SW Max2)
SW avg = √ (1 min. / 2 min. x 1/3 x 9662)

SW avg = 406 Watts
4. From Slipwatts vs rpm curves

The 50MB90B20 will dissipate 450 Watts at 360 rpm.

5. Select 50MB90B20.



Selection - Heat Dissipation (Slip Watts) vs. Speed Chart (RPM)

Chart 1