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 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.

## Magnetic Particle Brake for Controlled Deceleration 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.