Small VFD Issue

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
The motor FLA 17.2 /sqrt 3 = 10 A ??? ( from his choke sizing post )
the drive is only rated for 6.7 output on 1 ph input?

the max S for the drive at 230/3 is sqrt 3 x 230 x 6.7 ~ 2.7 kva
converted to 208/1 is 13 A drive input
call it 15 assuming the pump is fully loaded and some drive loss

if really power quality perhaps a cvt like a sola
will maintain V, isolate THD both ways, reduce line noise, etc
i don't think it is power related, magnitude or quality
You shouldn't put a feoresonnant CVT like a Sola ahead of a VFD unless it is over sized by at least 200%. Ferroresonnant transformers will flat-top the sine wave as you approach full rated current, which results in low DC bus voltage when it passes through the rectifier and extreme heat in the CVT.
 
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Ingenieur

Senior Member
Location
Earth
You shouldn't put a feoresonnant CVT like a Sola ahead of a VFD unless it is over sized by at least 200%. Ferroresonnant transformers will flat-top the sine wave at you approach full rated current, which results in low DC bus voltage when it passes through the rectifier and extreme heat in the CVT.
Sola makes xfmrs specifically for vfd use
after looking only 3 ph though
not sure if it is a fr type

still doesn't change the fact that it is loaded 50% over the mfgs spec

to sense a uv condition does a vfd sense the ac input or the dc bus?
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Sola makes xfmrs specifically for vfd use
after looking only 3 ph though
not sure if it is a fr type

still doesn't change the fact that it is loaded 50% over the mfgs spec

to sense a uv condition does a vfd sense the ac input or the dc bus?
Drives sense voltage on the DC bus, not the AC input. Only the DC bus voltage matters, which is why you can feed a drive with DC if you want to, as long as it's at the right voltage.

You are incorrect on it being under sized. The specific part number he posted is rated for up to 20.5A input, single phase. The output is rated for 3HP, 9.0A, but that's at 3 phase. That drive was designed to be fed with single phase, so it has larger diodes and more capacitance to deal with it.
 

Ingenieur

Senior Member
Location
Earth
Drives sense voltage on the DC bus, not the AC input. Only the DC bus voltage matters, which is why you can feed a drive with DC if you want to, as long as it's at the right voltage.

You are incorrect on it being under sized. The specific part number he posted is rated for up to 20.5A input, single phase. The output is rated for 3HP, 9.0A, but that's at 3 phase. That drive was designed to be fed with single phase, so it has larger diodes and more capacitance to deal with it.
is this the correct model number? Or do they make a dedicate 1 ph model?
this is directly from their manual
????



  1. Model KBDA-29 – Terminals “L1”, “L2”, “L3” – Designed for single-phase or 3-phase AC line input.Rated for 208/230 Volt AC line input only. Rated for 2 HP maximum with single-phase AC line input(Terminals “L1”, “L2”) and 3 HP maximum with 3-phase AC line input (Terminals “L1”, “L2”, “L3”).


  1. Model KBDA-29 – Has a maximum rating of 9.0 Amps (3 HP (2.25 kW)) when used with a 208 – 230Volt 50/60 Hz 3-phase AC line input. When used with a 208 – 230 Volt 50/60 Hz single-phase AC lineinput, the maximum rating of the drive is 6.7 Amps (2 HP (1.5 kW)). Be sure to reprogram MotorCurrent (Function No. 0.01) to the actual motor nameplate current rating (not to exceed 6.7 Amps)

I stand corrected
they make a (1P) model set up for 1ph
9 A 3 HP

if his 17.2 derived for choke sizing is correct still ~10 A
but the motor is likely not loaded 100%

be curious for motor specs
rated V
FLA
code


 
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StarCat

Senior Member
Location
Moab, UT USA
KBDA-29-1P [Single Phase input only]
The drive is rated for 9A continuous.
The Motor SFA is 10.2
We run about 8.5 and the over current function will lock the unit out quickly if the Brewery boys get their valves out of position.

Kwired correct the enclosed 3PH unit that I saw was from another vendor....
So by the numbers this one was close to in range:
http://www.electricmotorwholesale.com/TCI-KDRB22LC1.html

Jraef spot on, easier than building out something with vents although I like the clean design of the single phase unit for the usage the vented one will be much easier to install.

All information is appreciated.

Thanks Guys

Warren
 
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