VFD The noise associcated with them

[FrancisDoody]

I was wondering what causes the noise generated by a motor connected to the VFD. The Hitachi SJ200 was tied into the system by simply disconnecting the T1/T2/T3 from the motor starter and connecting the input leads from the SJ200. The output leads were connected to the motor leads. The noise is the complaint. The load is a 3 Phase 5 HP exhaust fan. Can the noise be reduced? Should the motor starter have been removed during the installation. Is overload protection part of the VFD circuitry.

Thanks

 

[charlietuna]

What type of noise are you complaining about--- electronic noise--audio noise? Did you read the manual concerning noise reduction ?

 

[Fulthrotl]

I was wondering what causes the noise generated by a motor connected to the VFD. The Hitachi SJ200 was tied into the system by simply disconnecting the T1/T2/T3 from the motor starter and connecting the input leads from the SJ200. The output leads were connected to the motor leads. The noise is the complaint. The load is a 3 Phase 5 HP exhaust fan. Can the noise be reduced? Should the motor starter have been removed during the installation. Is overload protection part of the VFD circuitry.

Thanks

normally, VFD's provide ramp up and soft start capabilities that would be
cancelled by putting them behind an across the line starter, yes?
i was curious why you'd put one downstream of a contactor......

 

[K2500]

I was wondering what causes the noise generated by a motor connected to the VFD. The Hitachi SJ200 was tied into the system by simply disconnecting the T1/T2/T3 from the motor starter and connecting the input leads from the SJ200. The output leads were connected to the motor leads. The noise is the complaint. The load is a 3 Phase 5 HP exhaust fan. Can the noise be reduced? Should the motor starter have been removed during the installation. Is overload protection part of the VFD circuitry.

Thanks

As a rule VFD's don't like sudden interuptions in power supply.

This might help. the 8th cation/warning on page ii, says to use overloads with the drive.

Are you talking about the high pitch noise the motor itself makes?

 

[Besoeker]

I was wondering what causes the noise generated by a motor connected to the VFD. The Hitachi SJ200 was tied into the system by simply disconnecting the T1/T2/T3 from the motor starter and connecting the input leads from the SJ200. The output leads were connected to the motor leads. The noise is the complaint. The load is a 3 Phase 5 HP exhaust fan. Can the noise be reduced? Should the motor starter have been removed during the installation. Is overload protection part of the VFD circuitry.

Thanks

If you mean audible noise, it is most likely the PWM switching frequency. This is usually in the kHz region. On most VSDs you can adjust that. The link that K2500 kindly provided says the adjustment range for the Hitachi SJ200 series is 2kHz to 14kHz. Maybe changing that would make the noise more acceptable but note that de-rating may be required at higher frequencies.

 

[Strahan]

There is such a phenomenon called the reflected wave phenomenon, that is caused by the fast switching times of the IGBT's combined with the capacitance in long runs of motor power cables.These fast switching IGBT's also help generate harmonics on the motor cables. Most recommendations are to install line reactors and filters to the drive, motor cable, and motor installation to reduce the reflected wave.
Some drives have algorithms built into there software that detects and reduces the effect of reflected wave.
From the specs. I have read most manufacturers recommend installing reactors and such when cable lengths exceed 30ft. Reflected wave phenomenon causes the output voltage to nearly double.

 

[mtfallsmikey]

As far as audio noise from motors w/VFD's...my cooling tower fan motors have little, elevator motors have some, but since they are ramping up/down in speed, it's not really an issue.

 

[charlietuna]

Many VFD manufacturer's will double the warentee if you install reactors in the feed or they will be built in by the manufacturers. We always order that option or install separate reactors with every install. I think the noise your complaining about is from the motor -- a frequency switching noise which can be adjusted in the drive program -- it will not go completely away -- but it lessens it somewhat. On fans the noise is carried thru the duct system and then transmitted into the building .