Thread: Clearvue Max Amps?

Look on the motor name plate and it will tell you the rated current for the motor.

A motor can nominally operate for a brief period at a current above its rating, what "brief" and how much excess current depends on the motor.

How much does the current increase by as it becomes loaded up?

Provided the VFD is correctly programmed the VFD should take care of any overload problems and cut the power to the motor when that current is exceeded.

Hi Barry, if it's the standard Teco motor and Powtran VFD supplied with a clearvue then my experience / measurements are that the actual amp draw from the wall is very very close to double the indicated amp draw on the vfd. At 60hz mine indicates 4.5amps closed and up to 9.5amps open (so 9amps and 19amps from the point respectively).

The VFD indicates amps per phase not total and mine also seems to read about 20% lower than it theoretically should, or there are losses through the VFD. I assume the latter.

The motor is rated at 10amps per phase from memory or 17amps total.

Cheers, Dom

Originally Posted by DomAU

Hi Barry, if it's the standard Teco motor and Powtran VFD supplied with a clearvue then my experience / measurements are that the actual amp draw from the wall is very very close to double the indicated amp draw on the vfd. At 60hz mine indicates 4.5amps closed and up to 9.5amps open (so 9amps and 19amps from the point respectively).

The VFD indicates amps per phase not total and mine also seems to read about 20% lower than it theoretically should, or there are losses through the VFD. I assume the latter.

The motor is rated at 10amps per phase from memory or 17amps total.

Cheers, Dom

The difference is mainly due to motor inefficiency, the VFD only uses a few % of the current.

I went back to what I'd measured when I first put in my clearvue and the VFD display seems to read correctly for the current per phase that the VFD outputs to the motor (measured 8.8amps out when vfd was displaying 8.6amps) but the input current from the wall was a fair bit higher than the theoretical 1.732 x per phase amps. Not sure what the root cause of this was/is but the single phase current into the vfd was nearly double the displayed ouput current per phase from the VFD (which itself measured quite accurately as already stated). 18.05amps single phase in vs 8.8amps per phase out.

Originally Posted by DomAU

I went back to what I'd measured when I first put in my clearvue and the VFD display seems to read correctly for the current per phase that the VFD outputs to the motor (measured 8.8amps out when vfd was displaying 8.6amps) but the input current from the wall was a fair bit higher than the theoretical 1.732 x per phase amps. Not sure what the root cause of this was/is but the single phase current into the vfd was nearly double the displayed ouput current per phase from the VFD (which itself measured quite accurately as already stated). 18.05amps single phase in vs 8.8amps per phase out.

8.8A X 1.73 / 0.85= 17.9A

the 0.85 is the combined (in)efficiency of the motor and the VFD.

Originally Posted by BobL

8.8A X 1.73 / 0.85= 17.9A

the 0.85 is the combined (in)efficiency of the motor and the VFD.

Wouldn't the efficiency of the motor only relate to the power output for a given power input? The current drop across the vfd couldn't have anything to do with the motor efficiency could it?

Originally Posted by DomAU

Wouldn't the efficiency of the motor only relate to the power output for a given power input? The current drop across the vfd couldn't have anything to do with the motor efficiency could it?

The current drop by the VFD is small.

Motor efficiency is the wrong term. It's related to the real and imaginary currents that occur in an electric motor. My understanding of what happens is the motor inductance causes a phase shift between the input current (at the wall) and the current that the motor impedance allows to pass though the motor coils. To correct for this the current though the coils has to be divided by a further cosine of the phase difference. The cosine of the phase difference will sometimes be shown on the motor name plate and 0.85 is a common value. I may have this the wrong way around - really bad flub at the mo - can't think straight.

Thanks for the replies, it is the Telco and Powetran VFD, the motor is running at 50Hz.
All gates closed 2.8 amps all gates open 3.8 amps.
It seems there's no need to worry at these low figures.

Cheers Barry

Originally Posted by mannum3

Thanks for the replies, it is the Telco and Powetran VFD, the motor is running at 50Hz.
All gates closed 2.8 amps all gates open 3.8 amps.
It seems there's no need to worry at these low figures.

Cheers Barry

Wow. That is very low. Something doesnt seem right to me...

Originally Posted by mannum3

Thanks for the replies, it is the Telco and Powetran VFD, the motor is running at 50Hz.
All gates closed 2.8 amps all gates open 3.8 amps.
It seems there's no need to worry at these low figures.

Cheers Barry

Barry, the gate open numbers seem to be too low even at 50hz, what size ducting are you using and are the machine ports opened to 150mm?

You have zeroed in on the problem, I was away for 8 weeks, I had put up 225mm and 150mm piping, 150mm gates, a short length of 150mm flexy with a Bell mouth hood 150/200mm.

The cyclone outlet was a short bend, no filters.

Image my shock and horror on my return to find the cyclone had been fitted with extremely restricted/obstructed "muffler", the 150mm flexy and Bell mouth hoods removed, replaced with 100mm & 75mm flexy, plastic gates you can hear leaking.

"They" say its working, I say "Look at the Amps, its not working, its totally restricted"

I just checked mine out of curiousity (mine is a CV1800 with 16" CVMax impeller). With gates closed at 50 Hz VFD reads 4.75 Amps (interestingly this is higher than at 60 Hz of 4.4 Amps) and with a gate open it reads 6.5 Amps at 50 Hz.

Originally Posted by mannum3

You have zeroed in on the problem, I was away for 8 weeks, I had put up 225mm and 150mm piping, 150mm gates, a short length of 150mm flexy with a Bell mouth hood 150/200mm.

The cyclone outlet was a short bend, no filters.

Image my shock and horror on my return to find the cyclone had been fitted with extremely restricted/obstructed "muffler", the 150mm flexy and Bell mouth hoods removed, replaced with 100mm & 75mm flexy, plastic gates you can hear leaking.

"They" say its working, I say "Look at the Amps, its not working, its totally restricted"

Is this at a Men's Shed? I assumed it was in your workshop/garage. I assume the people that changed things just didn't understand anything about dust collection / fluid dynamics.

Yup