9 replies to this topic

[marke]

Anybody got ideas on good techniques and filters for reducing the harmonics produced on the supply by large drives? Lots used in rural areas for irrigation and resultant supply distortion is causing problems.

[gogo]

http://www.drivesurv...m?feature_id=61

[burus]

Yes, I do, but I need more information.

[marke]

One solution that I have come up with is to use a drive with a regenerative front end. (Active front end)
This essentially comprises two inverters, on on the input and one on the output. The input inverter or active rectifier, ensures that a sinusoidal current is drawn fom the supply. In a regernerative installation, this enables the regenerative energy to be fed back into the supply.

[leeeetao]

;)Maybe We can help

low voltage harmonic filtering device (the structure as shown in fig) is a special passive filter for 5 times (250HZ) and 7 times (350HZ) harmonic low voltage power grids. This is used for some enterprises such as medium-frequency smelting, variable frequency and rectification etc. it constitutes serial resonance absorption with inductance and capacitance so that the harmonic current can be kept from returning to power transformer. In this case, it can greatly reduced the harmonic quantity of grids, power loss , and improved the reliability of equipment and the other electrical equipment as well as be in favour of operation of power transformer to user. In addition, it also provides reactive power compensation with 120KVAR fundamental harmonic (50HZ) and improves the operating efficiency of user load.
Performing Q/TSH12-20001.IEEE-519

[marke]

Hello leeeetao

Can you point to a source of more information? web link or similar?

Best regards,

[mariomaggi]

Can you point to a source of more information? web link or similar?

Mirus
is one of the most specialized company in the world for harmonic filters, on their website there are a lot of technical information.

Kindest regards
Mario

[Tim]

The solution used in industrial servo-motor drives to reduce supply current harmonics, and to reduce the reservoir capacitor value, is to include an active PFC boost converter in the rectifier circuit. This is similar to the regenerative front end mentioned in a previous response.

If you guys are interested in learning more about active PFC for small variable frequency drives, International Recitifier and Fairchild Semiconductor probably have some useful info on their websites:

http://www.irf.com/p...mps/fs8383.html
http://www.irf.com/p...esktop/pfc.html

Though it's for a internal permanent magnet motor drive, this shows a VSD with an active pfc front end:
http://www.irf.com/p...tionaircon.html

http://www.fairchild...ts_new/pfc.html
http://www.fairchild...AN/AN-42047.pdf

When thinking about passive harmonic reduction I was looking at building a rectifying front end for a small (< 1 HP) inverter with resistors or thermistors included to reduce the high spike currents and slow the charging time constant of the reservoir capacitors. This reduces the bus voltage on higher loads, and increases drive losses (deliberately) but in our case, where the high harmonics of a direct rectifier cause us to fail EMC regulations, it is worth considering as a solution.

Tim

[hotvp]

Mirus
is one of the most specialized company in the world for harmonic filters, on their website there are a lot of technical information.

Kindest regards
Mario

Schaffner also have a new range of passive and active filters for use with drive systems which are pretty impressive. The active units also allow active power factor correction and phase angle correction.