250 rpm Synchronous Motor 9904 111 31813
The 31813 series low speed synchronous motor is a development of the
standard industrial series specifically designed for use in high quality
record decks that utilise the belt drive principle.
Particular attention has been given to the magnetisation of the 24 pole
rotor to optimise smooth running. This, together with the high accuracy of
stator pole placement minimises torque ripple and provides low audible
noise.
The motor which is designed for mounting horizontally with output shaft
vertically up is provided with an increased shaft length and a 3 mm
diameter to aid the fitting of the drive pulley. When fitting the drive pulley
the shaft rear end should be supported to ensure that the axial load
limitation is not exceeded.
The windings have been specifically designed to facilitate dual voltage
operation, a 6.8K Ohm resistor being used in series when operation from
a 220 Vac supply is required.
Dimensions mm.
Specification
Nominal Voltage Vac 110 Max Working temperature deg. C 105
Permissible voltage fluctuation %-15 / +10 Ambient temperature range deg. C -5 to +70
Supply Frequency Hz 50 Torque derating %/ OC0.25
Speed @ 50 Hz rpm 250 Insulation according to CEE10 Class 2
Direction of rotation reversible Insulation test voltage V2500
Direction control capacitor µ F 0.22 ( 250 Vac ) Maximum radial force N 5
Input Power W1.8 Maximum axial force N1.5
Input current mA 18 Mass g16
Housing zinc plated Bearings slide
Connections
Mclennan Servo Supplies Ltd. Tel: +44 (0)8707 700 700 www.mclennan.co.uk
110 V ac-50Hz : C=0.22µF :speed = 250 rpm 220 Vac 50 Hz: C= 0.22µF speed = 250 rpm
117 V ac-60Hz: C= 0.18µF :speed = 300 rpm
GREY GREY
RED BLUE
CW CCW
GREY GREY
RED BLUE
CW CCW
6.8KΩ
2.5W
23.9 14.2 ∅ 3.7
2.6
1.5 Mounting Flange
may be removed
on request
-0.002
∅ 3 -0.008
70.5 ∅ 51
60.2
∅10
1 175
Record deck Motor installation
Mechanical installation
Although the diagram shows a typical
installation there are a number of methods to
obtain optimum low vibration that will depend
on the design of the record deck. Although
the motor has been specifically designed to
generate low vibration, as a general guide it is
recommended that it is mounted to the motor
board via an anti-vibration pad as shown.
Since the pulley design of some record decks
impose a vertical force on the motor shaft the
motor shaft is not preloaded axially within the
motor. In some installations it will be
necessary to apply a a slight pre-load to the
shaft so that it runs in the fully ‘up’ position.
This is best achieved by means of a rubber
strap and a small cup that holds the shaft in
the fully up position as shown
Electrical installation of motor
Reducing motor vibration by means of additional trim circuit
The optimum torque provided by the motor should only be sufficient to accelerate the platter to synchronous speed,
since the lower the motor torque is during fixed speed operation, the lower the vibration inducing torque ripple will be.
For a given installation it may be possible to increase the value of the series resistor ( nominally 6.8 Ohms ) in the basic
circuit to optimise motor performance while a lower value of the phasing capacitor ( nominally 0.22 µF ) may prove
beneficial. For optimum results trimmers may be added in series with each motor coil to electrically balance the motor.
Platter
Rear shaft support
Basic connections Connections for reduced vibration
220 Vac 50 Hz: C= 0.22µF speed = 250 rpm
GREY GREY
RED BLUE
CW rotation
6.8KΩ
2.5W
GREY GREY
RED BLUE
Coil balance
trimmers
6.8KΩ
2.5W
Mclennan Servo Supplies Ltd. Tel: +44 (0)8707 700 700 www.mclennan.co.uk
