Graham_Wright
Well-Known Member
Most references are to field excitation. Is this standard? Tony Brooks shows the "ignition light" connection to the rotor.
Alternator exciter connection.
- Thread starter Graham_Wright
- Start date
VicS
Well-Known Member
Traditionally the ignition warning light provided the current for the initial excitation of the field coil which is the rotor. Once the machine is "up and running" it supplies its own field current via the field diodes and the regulator
Tony Brooks diagram shows the basic setup up
http://www.tb-training.co.uk/images/Image138.gif
Last edited:
Graham_Wright
Well-Known Member
Traditionally the ignition warning light provided the current for the initial excitation of the field coil which is the rotor. Once the machine is "up and running" it supplies its own field current via the field diodes and the regulator
Tony Brooks diagram shows the basic setup up
Probably should have put that in as a link to avoid copyright infringement
Yes - you'll be in trouble with Tony!
However, the diagram is wrong. Clue - diodes.
Field I thought was stationary?
solent clown
RIP
a different way to illustrate the circuit than I remember, but I cant see what is wrong.
DickieT
Well-Known Member
Field does rotate in an alternator, inducing voltage into the stator encased in the outer shell. Opposite way round in a dynamo.
Bottom set of main output diodes are the wrong way round. Cathodes should face upwards to conduct on -Ve cycles.
Bottom set of main output diodes are the wrong way round. Cathodes should face upwards to conduct on -Ve cycles.
solent clown
RIP
yes, got it now, thanks. :encouragement:
Leighb
Well-Known Member
As a matter of interest, how is the alternator "excited" if there are no ignition warning lights? The only lights on my dash panel are to show when the glow plugs are on but no other lights, there is a warning buzzer which warns of low oil pressure/high water temp/no charge, this does sound until the engine fires would that serve the same purpose?
Graham_Wright
Well-Known Member
It is possible the oil pressure switch provides the exciter current (until the alternator spins and provides its own excitation via the in-built diodes) and you mention "no charge" which is what the ignition light normally is. The buzzer may be driven by an "OR" of all these things or the excitation current may be supplied just via a resistor.
MonniotC
Well-Known Member
On my Petter Mini-6 (AC1WM) installation, it's the oil pressure switch which supplies the exciter current (until the oil pressure comes up)
VicS
Well-Known Member
Well spotted!
VicS
Well-Known Member
lw395
Well-Known Member
Some alternators (and dynamo) will self start without the warning light.
It just relies on the remaining magnetism in the iron of the field setup. Lucas motorbike dynamos were typically like this.
When it gets old, you may have to give it a 'few' rpm for it to start up.
Many motorcycle alternators use permanent magnets and don't regulate via the field. They use series or shunt regulators.
Again the Lucas option was notably crude, a big Zener diode to clamp everything down to 'about' the right voltage.
It just relies on the remaining magnetism in the iron of the field setup. Lucas motorbike dynamos were typically like this.
When it gets old, you may have to give it a 'few' rpm for it to start up.
Many motorcycle alternators use permanent magnets and don't regulate via the field. They use series or shunt regulators.
Again the Lucas option was notably crude, a big Zener diode to clamp everything down to 'about' the right voltage.
