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) |
|---|---|---|---|
| 12 lbs. | 200 fpm | 3 in. | 30 in. |
1. Calculate Torque (T)
T = Force x Radius
T Start = 12 lbs. x 30in./24in = 15 lb. ft.
T Finish = 12 lbs. x 3in./24in. = 1.5 lb. ft.
2. Calculation Speed (RPM)
RPM = Velocity/π(diameter)
RPM Start = 200 fpm / π x 30in./12in. = 25 rpm
RPM Finish = 200 fpm / π x 3in./12in. = 255 rpm
3. Calculate Slipwatts (SW)
SW = T x RPM / 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 = 54 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 (RPM) | Time to Stop (t) |
|---|---|---|
| 1000 lb. ft.2 | 360 rpm | 60 sec. |
1. Calculate Required Torque (T)
T = WK2 (rpm) / 308(t)
T = 1000 (360 rpm) / 308 x 60 = 19.5 lb. ft.
2. Calculate Maximum Slipwatts (SW Max)
SW Max = T x RPM / 7.04
SW Max = 19.5 lb. ft. x 360 rpm / 7.04
SW Max = 997 Watts
3. Calculate Average Slipwatts (SW Avg)
SW Avg = √[(t on / t on + t off) x 1/3 x SW Max2)]
SW Avg = √ [(1 min. / 2 min.) x 1/3 x 9972)]
4. From Slipwatts vs RPM curves
The 50MB90B20 will dissipate 450 Watts at 360 rpm.
