asynchronous generator

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bwyllie

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MA
Dealing with a new cogen unit and the manufacturer states the unit is asynchronous and does not need parallel equipment so that it would be synched with the utility. Can anyone explain why that is?
 
There are two possible meanings.

1) An asynchronous generator is simply an induction motor operated with an 'overhauling load'. This means that the 'load' (in this case the mechanical prime mover of the cogen plant) pushes the motor faster than synchronous speed. The motor draws reactive power from the line to set up its magnetic field, but outputs real power to the line. Such a generator is automatically in synch with the mains supply, as long as the rotor is spinning anywhere around synchronous speed. You still need to deal with all of the problems associated with starting a large induction motor, and the motor speed still needs to be approximately matched to synchronous speed, but you don't need the precision matching of phase angle and frequency as with a synchronous generator.

2) The generator spins at whatever speed the prime mover pushes it at, and some sort of electronic power conversion system (rectifier-inverter set) converts the output to line synchronized output.

-Jon
 
Sounds like an induction generator which is a motor being driven by a prime mover. It can only produce power when connected to a source. It is locked into sync with the source.
don
 
Asynchronous usually means equipment operating at some undetermined or varying speed or frequency. An induction generator could be described as asynchronous since the prime mover speed can vary without affecting the frequency of the output voltage.

Note that if this cogen unit does use an induction generator, it cannot generate power unless it is connected to the utility. It won't keep lights on during a power outage like a standby power system.
 
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