inverter output harmonics suppression

[mhtavallaie]

Dear friends

as you know the low and high frequency harmonics produced by 3 phase inverters causes serious disturbance to sensors , microprocessor controlled circuits etc.

anybody willing to advise me on how to get rid of these disturbances is highly appreciated.

rgds
hadi

 

[JimB]

The quick answer is to throw out that crappy inverter and get a decent one!

A bit more detail would be useful.
What size inverter.
Is it powering the sensors and micro processor.
Is the problem due to noise being coupled into cables.
Is the instrumentation part of the inverter or a totally separate system?

JimB

 

[zkt_PiratesDen]

Speaking of inverters- the power company where I live seems to use this area a testing ground for their emengency switching equipment- and tests it quite frequently- sometimes daily. Ive lost more than one piece of work when the line voltage dropped to zero for just long enough to reboot the pc. THere outa be a law. Anyway, the last time it happened I ran out and bought a 700 watt (continous output) dc to 120ac inverter and borrowed the battery from the "project car". I leave the pc on allthe time. Got any idea how many amps I need to put into the battery to keep it charged.? Or how many watts your average pc and 17" crt monitor (with a burned out red gun driver transistor cause I havent got around to fixing it) draws ?

 

[stevez]

I've been doing some reading on the subject of switched mode power supplies - a related subject area. A couple of things that came up several times - that fast switching can improve efficiency- that fast switching can generate a lot of noise. I also read about semiconductor designs that switch fast but not too fast to strike a balance between efficiency and noise generation.

I don't know if you are in a position to affect the design of the inverters but I thought I'd share the information.

 

[mhtavallaie]

inverter rating

The quick answer is to throw out that crappy inverter and get a decent one!

A bit more detail would be useful.
What size inverter.
Is it powering the sensors and micro processor.
Is the problem due to noise being coupled into cables.
Is the instrumentation part of the inverter or a totally separate system?

JimB

dear colleague

the inverter is a 5.5kw driving a 3ph ac 380v motor and the interference is coupled into cables which disturb specially the adjasent sensors.the motor cable is also shielded .

rgds
hadi

 

[zkt_PiratesDen]

That doesnt sound so crappy at all. Could you measure the interference frequqncy on a scope an calculate the valve of an RC filter ? Guess youre sure the interference isnt coming from the motor.

 

[Analog]

Sounds like you need to do some filtering on both ends - the inverter's harmonics can be better suppressed with isolation transformers (costly). There are also filters for this application.

On the small signal side, the same thing, plus better filtering on the sensor level, and the power supply feeds to the uP etc.