Shaded Pole Motors
Our shaded pole motors cover two of our “ranges”; our 33 range and our 84 range. Shaded pole motors are widely used in industrial and commercial refrigeration, in condensing and evaporating units and even in small ventilating units. A shaded pole by construction is quite a simple motor and relatively cheap to produce, but they are not as efficient as say a PSC (Permanent split capacitor) motor. There are however a couple of PSC motors amongst the 33 range and 84 range. Due to their construction method they offer low start up torque which limits them to light fan applications.
Our 33 range of shaded pole and PSC (Permanent split capacitor) motors are manufactured in 2, 4 and 6 pole versions typically ranging from 4W up to 100W, the majority are single speed although some are multi-speed. They are visibly different from 84 range as they have a black round body which is 3.3” in diameter (84mm).
Our 84 range of shaded pole motors These motors are four shaded poles, single phase, running at a nominal tension of 230-240V, 50-60Hz with an output power ranging from 5 to 34 Watt; insulation class B and protection IP42. 84 range are a square motor body with cast aluminium end shields, the body diameter like 33range is 84mm.
Bearing type and quality is an important factor in determining the reliability and life expectancy of fractional horsepower electric motors and fans. The choice is generally between sleeve bearings and ball bearings. When choosing, design engineers must consider factors such as: application, fan longevity, mounting, angle of operation, noise, ambient temperature, duty, lubrication issues, etc.
When the ambient temperature is relatively low, sleeve bearing motors can last as long as ball bearing motors. However, sleeve bearing motors can have problems starting at very low temperatures due to the oil viscosity and bearing stiction – especially with low power models. Shaded pole motor designs are inherently inefficient and the surplus heat generated can help to free bearings in some cases.
Motor reliability is crucial in achieving long life. Small motors and fans operating in the range from 25 to 60 degrees centigrade using ball bearings will outlast their sleeve bearing equivalents by an average of 50 percent. Ball bearing motors can operate beyond 70 degrees centigrade, with reduced life, whilst sleeve bearing motors
Ball bearing motors can be mounted in any position without affecting life expectancy. Sleeve bearing motors are designed to operate with the shaft in a horizontal position and any variation in angle can reduce life span. Ball bearings are preloaded with a spring or wave washer during manufacturing. A ball bearing motor can be used with heavier fan blade when the shaft angle is vertical up or down.
Bearing End Float
Motors with ball bearings have no axial movement. The relative position between shaft and bearing is fixed. To allow for thermal expansion, sleeve bearing motors are manufactured with a clearance which ranges from 0.1mm to 1.0mm. This prevents the motor from seizing when it gets hot. This “end float” is not usually a problem, though exact fan positioning with ball bearings is preferable.
Ball bearings are manufactured using precision components. Steel balls are precision ground and super finished to provide exact tolerances. Sleeve bearings can deteriorate at high temperatures because they are made from porous powdered metals in a sintering process. Micro hardness makes secondary machining difficult. Sleeve bearing quality depends on shaft clearance and oil supply.