Commenting upon this because out-with most researcher fields.
The wonderful thing about thyristors is that they switch on within a
few microseconds -- but they don?t switch off unless driven by AC or
?commutated?. Thyristors are extremely robust, cheap and intrinsically
suitable for high voltage and high current, so find obvious
application in mains AC drills, the speed control being effected by
variable phase triggering. Low voltage DC is a different matter
because not only do they have to be commutated (which though
reasonably easy is not cost effective) the voltage drop also wastes
power. Consequently, most low voltage DC drill controllers employ
?pulse width modulation? (PWM) in various forms, the switching element
being a power transistor. You can actually hear some of them whistling
slightly as they switch. A ?rheostat? would waste too much power and
get horribly hot. More expensive too, and the torque at low speed
would be very poor. Some real cheap, low-power drills may use a
transistor, in essence as a variable resistance, but unlikely.
The ?G?, ?S? and ?D? on your ?thyristor? indicate Gate, Source and
Drain on a MOSFET -- a kind of transistor. If you read the number on
it you very likely can find the spec on the web. Since the control is
continuous, the trigger must incorporate a bunch of electronics in the
trigger in addition to the variable resistance control. Although it is
very simple to copy the circuit, or even design a new one, you need a
reasonable electronic skill level. However, though you don?t recognise
a (MOS)FET, you are clear, logical and accurate in your presentation
so you do have the basic wherewithal.
Presumably you don?t want to strip the parts from the drill and
incorporate them in a box. There may be single power chip devices
incorporating all the necessary gubbins but couldn?t find one with a
quick search. Data sheets for controllers which I found would probably
only confuse you so I didn?t post. If you are really desperate though
I could do a fuller search.
Frustrating, we can?t post pictures otherwise I could design one for
you, but post if you want further or deeper info.
Best |
