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.
5. Select 25MB90S.
Magnetic Particle Brake for Controlled Deceleration
| 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)
4. From Slipwatts vs rpm curves
The 50MB90B20 will dissipate 450 Watts at 360 rpm.
