At work today, we had a work tour of the flywheels; that I have previously mentioned;
The Flywheel Generator Converter (FGC) works in a similar manner to the alternator in a car, the rotating part of the Generator carries the poles which when energised will generate electricity. the rotor is 9 meters in diameter and weighs 775 tons, much of this mass is concentrated in the rim; this forms a large flywheel. The flywheel is an effective means of storing kinetic energy.
The Peak power requirements of each JET pulse exceeds 700MW. this amount of power can not be directly taken from the national grid. Therefore the generators are used to supply the additional electrical energy required.
Each Generator is capable of supplying 400MW of pulsed power.
This is the view of the Toroiadal coil, 8.8 MW pony motor and flywheel pit; this photo was taken from the control room, behind the yellow enclosure is the Vacuum breakers
The Main control pannel for both FGC; combining both Analogue controls; and PC automated controls (Running Fedora) these panels allow the Flywheel operators; to start the machines up to about 50% running speed, and at that point control is passed over to JET main control;
This is the entrance to the Poloidal FGC, you can see the Pony Motor on the right; the floor plates can be lifted to allow access to the pit below; there is a 50 ton gantry crane for maintenance use overhead.
In the flywheel pit there is a space round the flywheel itself that houses auxiliary systems; this includes the cooling fans for the flywheel.
This is a Photo inside the flywheel enclosure; on the right is the flywheel itself; a 775 Ton Iron Laminated Flywheel; the Red things at the top of the photo are the Strator windings; 48 Coils, that generate AC when the Rotor coils are energised.
The Grey lumps on the Flywheel are some of the 48 DC Rotor Magnets; DC Current is applied to the rotor coils via slip rings on the main axle,
A View under the Flywheel showing the bolts that hold the lamination together; as well as the 100Ton rated jacks used for maintenance. The grey panels with the two water pipes in them is a radiator; and then access to the thrust bairings behind, when the flywheel is stationary; all of its weight is supported on these bairings; to start it; Jacking oil is pumped between the base of the axle and the bairing, then the pony motor starts to power it to its working speed of up to 225 RPM.
When power is needed for a pulse, the rotor windings are energised and the rotational energy is converted into electrical energy, causing the flywheel down to 112 rpm.
On start up, it takes the 8.8 MW pony motor about 20, to 30 minutes to spin the Flywheel up to speed. during a pulse each Flywheel Generator Converter can provide 2,600 MJ of energy with a duty cycle of 20 seconds of pulse power, per 10 minuets @ 67kA
Anther look under the flywheel; here you can see the grey ‘spider’ the rim is attached to.
This is one of the 18 little 100 ton jacks used to lift the flywheel during maintenance;
This is one of the four AC to DC converters, around the outside of the FGC that takes the AC from the Stator Coils; and turns it into DC for JET, the white tubes are fuses; and behind them, are a bank of Diodes.
This is the where the Red bus bars leave the stator; and enter the AC to DC converter. the small cables leaving the converter are diagnostic and sensor cables.
One of the Pony motors, (the top grey box).
Some Toroidal field (TF) coils that have not been used in JET. the coils are ‘D’ Shaped, this is to minimise bending stresses due to in-plane forces, it also allows them to fit the elongated shape of the plasma and vacuum vessel.