rulmeca 80LS Manual De Instalación Y Mantenimiento página 9

Actual full load belt speed is almost never exactly equal to nominal belt speed.
Actual belt speed is a function of the motor pole numbers, gear ratio and load. The RULMECA catalogue displays the
nominal belt speed at 50Hz.
Note that all belt speeds shown in the RULMECA catalogue refer to un-lagged pulleys because:
1. Belt speed for each model is a function of pulley diameter,
2. Pulleys are available with and without lagging,
3. Lagging changes the pulley diameter,
4. Various lagging thickness are available.
Note that each RULMECA motorized pulley for a three-phase power supply uses an asynchronous squirrel cage
induction motor with about 5% slip. In a no load condition, motor RPM is nearly equal to "synchronous speed" RPM.
The slip rate is dependent on power and design of the motor.
Low powered motors have a lower slip rate than high-powered motors. At full load, the motor RPM is about
5% less than synchronous.
Pulley by pulley the "nominal belt speed" displayed in the RULMECA catalogue is based on un-lagged pulleys
running at full load, nominal voltage (e.g. 400V) and 50Hz.
The nominal full load belt speed of a lagged pulley running at
1.
Full load,
2.
Nominal voltage (e.g. 400 volts),
3. 50 Hz equals the nominal full load belt speed specified in the RULMECA catalogue, times the ratio of the lagged /
un-lagged pulley diameters.
Example: A 4.0kW motorized pulley 320M with an un-lagged pulley diameter of 321mm has a nominal belt
speed of 0.8m/sec. The actual belt speed is a function of
• The rotor speed (RPM),
• Gear ratio,
• Shell diameter and
• Load.
E. g. the above mentioned 320M with a nominal belt speed of 0.8m/sec. has
1. A gear ratio of i = 28.6,
2. A rotor speed of n = 1440min
3. A shell diameter of 0.321m,
The actual belt speed at full load is
π
V(m/sec) = x d (mm) x RPM (1/min) / 60 x i
π
= Pie,
d = pulley diameter,
RPM = revolutions per minute,
i = gear ratio
v = 3.14 x 0.321m x 1440min
If this pulley is supplied with 10mm thick lagging, the belt speed of the lagged pulley equals 0.85m/sec. x
(0.341m/0.321m) = 0.90m/sec. at full load, nominal voltage and 50Hz.
m) Ambient Temperature:
Motorized pulleys are normally cooled by dissipating heat through contact between the surface of the pulley and the
conveyor belt. It is essential that each pulley have an adequate thermal gradient between the pulley's motor stator
and its ambient operating temperature.
All motorized pulleys in this catalogue are designed and tested under full load without rubber lagging for a use in a
max. ambient temperature of +40°C. degree.
Rubber lagging and/or higher ambient temperatures than +40°C (100F) as well as conveying hot material will
reduce the heat transfer from the electrical motor through the pulley body to the air and/or the conveyor belt.
This will always switch off the motor winding protection switch and could possibly end-up in a burned motor
winding.
,
-1
/ 60 x 28.6 = 0.85m/sec.
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EN