brushless motor rectifying

[Jamie Morken]

Hi,

If you have a wye wound brushless generator and rectify it with a 6
diode full wave rectifier, or if you rectify it with a 3 diode half wave
rectifier with the wye common being ground, the voltage of the 6 diode
rectifier will be 1.77x that of the 3 diode rectifier I read, assuming
it is a 1kW generator normally fullwave rectified is it safe to still
extra 1kW of energy using the 3 diode rectifier configuration, or will
the extra current required possibly overload the generator?

Jamie

 

[Mook Johnson]

Hi,

If you have a wye wound brushless generator and rectify it with a 6
diode full wave rectifier, or if you rectify it with a 3 diode half wave
rectifier with the wye common being ground, the voltage of the 6 diode
rectifier will be 1.77x that of the 3 diode rectifier I read, assuming
it is a 1kW generator normally fullwave rectified is it safe to still
extra 1kW of energy using the 3 diode rectifier configuration, or will
the extra current required possibly overload the generator?

Jamie

Probably will not work. Taking 2KW form a 1KW genertor will likely cause
loverload.

 

[Jamie Morken]

Probably will not work. Taking 2KW form a 1KW genertor will likely cause
loverload.

Sorry I meant to say:

is it safe to still EXTRACT 1kW of energy using the 3 diode rectifier
configuration

 

[Mook Johnson]

Sorry I meant to say:

is it safe to still EXTRACT 1kW of energy using the 3 diode rectifier
configuration

I don't think that can be ansewered without knowing the generator. If you
pulling the same power with at 1/1.77 lower output voltage, the current must
be a factor of 1.77 higher. (by 1.77) Thats ~ 3 times more I2R heating of
the winding in the generator.

If the generator runs cool at 1Kw with the a full wave diode bridge, it
might be worth a shot. If it gets warm - hot to the touch. fagitaboudit.

 

[Tim Wescott]

I don't think that can be ansewered without knowing the generator. If you
pulling the same power with at 1/1.77 lower output voltage, the current must
be a factor of 1.77 higher. (by 1.77) Thats ~ 3 times more I2R heating of
the winding in the generator.

If the generator runs cool at 1Kw with the a full wave diode bridge, it
might be worth a shot. If it gets warm - hot to the touch. fagitaboudit.

More like 1.5 times the heating, because it'll be three times more, but at
50% duty cycle in each coil.

You'd want to check to make sure you don't saturate the iron, too.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

 

[Jamie Morken]

More like 1.5 times the heating, because it'll be three times more, but at
50% duty cycle in each coil.

You'd want to check to make sure you don't saturate the iron, too.

What would saturating the iron do when running as a generator? Its not
like a motor that would draw more current I think.

cheers,
Jamie

 

[colin]

Hi,

If you have a wye wound brushless generator and rectify it with a 6
diode full wave rectifier, or if you rectify it with a 3 diode half wave
rectifier with the wye common being ground, the voltage of the 6 diode
rectifier will be 1.77x that of the 3 diode rectifier I read, assuming
it is a 1kW generator normally fullwave rectified is it safe to still
extra 1kW of energy using the 3 diode rectifier configuration, or will
the extra current required possibly overload the generator?

Jamie

it has twice the current in each phase,
but only for half the time,
but dissipation rises with square of current,
so the heating due to current will be double.

if im not mistaken you should be able to draw x 1.4 the current in the 3
diode config
with no extra heating due to current.

but if the windings are over specified - wich would be uneconomical -
I cant see any other problems.

but then diodes are a heck of a lot cheaper than replacement generators.

if you want lower voltage can you connect it in delta config ?

Colin =^.^=

 

[Mook Johnson]

What would saturating the iron do when running as a generator? Its not
like a motor that would draw more current I think.

cheers,
Jamie

The windings would no longer support the the BEMF since thieir inductance
dropped and the voltage output will drop off until the coreomes out of
saturation. Massive distortion of the output waveform as well.