Van De Graff Large 300mm Diameter Variable Speed 240V
This 300mm diameter Van De Graaff is a special model with a special large ball for customers that must have the biggest.
Please note that the standard “large” series Van De Graaff unit in the range is 250mm diameter ball. The ball mounts on an insulation tube that protects the belt, however the bottom of the belt and the top of the belt are both accessible including both combs. The belt is a long lasting silicone rubber and the performance and reliability is excellent.
The whole unit is easily dismantled down to separate components for convenient transporting.
The base of the instrument is now more compact and the drive system is separate and removable from the base. If a VDG should require repair, only the drive can be sent to IEC instead of the complete unit. A big saving in freight cost.
Principle of Operation
The rubber belt is driven by the plastic pulley and a charge is induced on the surface of the belt as the rubber belt leaves contact with the plastic pulley. Negative electrons jump from the belt to the
earthed comb to cause the belt surface to become positive potential.
The belt carries the charge to the dome. The inside surface of the belt touches the metal pulley to become the same potential as the dome and the positive charge across the belt thickness is removed from the belt by the sharp points of the upper ‘comb’. This charge from the belt adds to the dome’s existing charge so that the charge rises over time.
The outer surface of the dome acquires an increasing positive charge in respect to earth. This ‘charge pumping’ effect continues until a voltage on the large dome is sufficient to cause a spark
discharge between the dome and the discharge ball.