Gday Matthew
Thanks for your reply,esp about the definition of a thyristor
and its use in Oz
Cheers, Mick
On 16/03/2024 2:44 pm, 'Matthew Geier' via TramsDownUnder wrote:
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> NSWGR 85 and 86 class locomotives were 'cam shaft' control. At the time of their construction high power high voltage GTOs didn't exist yet. I believe that the two classes were broadly similar, except that the 86 pilot motors could 'back notch', the 85 class couldn't, so when connected, the 85 class had to lead lest a driver in an 86 class use the back notch feature, forgetting the 85 in the shafts and then have the two types in different notches. I believe what would happen is the 86 would back notch - but the 85 class would cut off and try to notch back up, resulting in all load transferring to the leading 86 while the 85's cam shaft did a full revolution to the selected notch. Meanwhile the 86 class would overload and either trip itself, or pull the substation.
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> Sydney trains foray into electronic drive was the 'C' sets (originally referred to as chopper Ks, as they were targeted 'K' initially). I gather they were the first implementation of then new Mitsubishi 1500v Gate-Turn-Off Thyristor. Prior to that no single thyristor could switch such a high voltage so they had to be 'stacked', but then you had synchronisation issues in the stack. (If they didn't stay in perfect synchronisation, they would tend to blow up).
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> The GTO is a DC device, a simple 'thyristor' switch as found in say a incandescent dimmer switch, is an AC only device.
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> The Cs were sort of prototype Tangaras. The Tangara's having a Mitsubishi GTO traction package. The traction motors were the 'old school' DC series motors. I think they were in permanent series-parallel. I've not heard of any chopper train having a transition. Doesn't mean some one some where didn't do it though.
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> The Variotram has a Variable Voltage Variable Frequency or 'VVVF' drive to an AC induction motors using Insulated Gate Bipolar Transistors. The ill fated Tangara G7 also had a VVVF drive, sort of being a prototype for the following G sets. The Variotram motors were in parallel pairs, with each VVVF stack driving a parallel pair of motors - one of each side of the bogie frame giving the motor bogie a sort of virtual axle as the wheel motors on each side were frequency locked to each other being driven from the same VVVF stack.
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> All modern rolling stock, both heavy and light rail, now uses VVVF drives to AC motors. The motors are usually 3 phase induction motors and but sometimes now they are permanent magnet motors. I don't think any one us Aus has yet made the foray into using permanent magnet traction motors yet. (They are more efficient, but you can't play games with the field strength easily, so they are not suitable for all applications.)
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> On 16/3/24 07:23,billbolt...@... wrote:
>> A thyristor is *a four-layer semiconductor device* (that is, it is explicitly not a diode or transistor) consisting of alternating P-type and N-type materials (PNPN). A thyristor usually has three electrodes: an anode, a cathode and a gate, also known as a control electrode. The most common type of thyristor is the silicon-controlled rectifier (SCR).
>>
>> Off the top of my head... the NSW "C" and "T" suburban sets use chopper control systems and also the 85 class electric locos and the SLR VariotramsIn VIC the Z3, A, B and W8 trams and some Comeng suburban cars also use chopper control.
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>> I'm sure others may know of further examples.
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>> On Saturday 16 March 2024 at 03:06:43 UTC+11 Mick Duncan wrote:
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>> Gday All
>>
>> Between series parallel K,camshaft and unit remote control and
>> VVVF of
>> today, there is Chopper control.
>>
>> Some questions.Were there some Chopper controls with
>> series,parallel
>> as the dwgs Ive seen have all the motors in series
>>
>> Is the Thyristor a diode with a base that can have its resistance
>> changed by a 3rd wire input so it can conduct or not
>>
>> What Oz trams and Sparks had Chopper control
>>
>> Cheers, Mick
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