Re: (ET) rotary inverter specifics

["The Nauglers" <snaugler earthlink net>]

Thon,

The rotary inverter will have a sine wave output.  The only reason an
induction motor may not like the rotary inverter would be how good the
voltage regulation was.  This includes both continuous voltage output
stability and the capability to handle inrush, or starting, currents and 
the
voltage drop that occurs when that inrush to your load happens.

It is possible that a rotary inverter may not handle the starting current 
of
your induction motor.  If the inrush capability is too low the output
voltage will drop, and sometimes the inverter will slow down and the
frequency will also drop.  In either case that is bad for both the inverter
and the motor you are trying to run, and frequently you can't even get the
motor to start.

While more often a flaw in the ratings of electronic inverters, you need to
make sure that your rotary inverter has the following two specifications:
1.  A continuous current output that meets or exceeds the continuous draw 
of
your inductive (motor) load.
2.  A surge, inrush, starting, or peak current rating that is at least 
three
to five times the running current of your inductive load.  It only has to
maintain this higher current for two to five seconds, as long as it takes
the inductive load to reach normal operating conditions.

This rating applies to generators too.  I had a friend whose well pump 
would
not start when run off a Coleman 4000 watt generator.  That same well would
start and run off a Honda 3500 watt generator.  The lower watt rated Honda
had a higher ability to handle the well's inrush starting current.

There are some military rotary inverters out there with a 400 Hz output, so
beware of them.  A load designed for 60 Hz operation will not run off of
them, but many unversal motors will.

Steve Naugler
snaugler earthlink net

----- Original Message ----- 


> Could someone explain why a 2250W rotary inverter would not "operate
> induction type motors found in fans, furnace blowers, washers, dryers,etc
".
>
> Thanks.
> Thon