Nola Type Energy Savers And Harmonics

[kens]

Hi all, has anyone had a chance to study the harmonic caractaristics of these devices? I would be interested in any experiences or measurements.

 

Thanks

 

Ken

[marke]

Hi Ken

 

Many years ago, when this technology was in it's infancy, I had some tests done by Canterbury University, Christchurch MED, ERA labs (UK) and SEC Vic.

All of these tests indicated that there were no undue concerns at that time.

I do not have copies of the test results unfortunately as these remained with a previous employer.

 

If the technology is used correctly, it will only be applied to motors with low power factors and the inductance of the motor behave as a filter. The harmonics are Odd order and primarily below the seventh harmonic.

Perhaps one of the manufacturers, i.e. Somar Powerboss may be able to give you actual figures.

 

Best regards,

Mark.

[jraef]

A few years ago we did a study in conjunction with an IEEE committee member in response to a customer inquiry, but not for the Nola versions, just for regular soft starters. Here is an excerpt from my report at the time.

 

THD Levels

Given the RVSS starter's transitory nature of operation and use, the percentage of Total Harmonic Distortion (% THD) created is difficult to quantify. Generally, THD during soft starting is the worst at mid range firing angles, with the highest percentage being at the 90º point (50% output). Voltage THD can be as high as 20% at this point. THD decreases rapidly as the firing angle increases however, becoming insignificant (less that 5% Voltage THD) at around 80% output. Most applications will start acceleration at an Initial Torque Level of 50 - 60% output, and accelerate to 80% within 15 seconds or less. With this in mind, RVSS starters meet the requirements of IEEE-519-1992 in most cases without the need for any external filtering.

 

This report was based on an analysis done by a PE we hired. Unfortunately I don't think I can get hold of that specific report any longer, it was done in 2003. But here is a report he wrote earlier describing his modeling method (in MathCAD). At the end of this paper is a chart that provides THD values at any given firing angle. What you don't know is what the firing angle of the Nola controller is going to be. It is fairly low however, so generally the THD is going to be low as well.

 

http://www.geocities.com/thomas_b_34654/toshiba1.pdf

[kens]

Thanks for the prompt replies This was really for interest more than any thing else. I was on a site recently and there were a several of these devices and also multiple VSDs. I noticed that when the motors controlled by the energy savers started there was a considerable short term increase in current harmonic (as to be expected during the start period) but this made me wonder what the units were doing when they were 'economising'.

 

 

Cheers

Ken

Doc2.doc (Graph of current harmonics at mains switchboard)