35 replies to this topic

[marke]

Anybody had any experience with medium voltage soft starters??

[Damjan]

MV soft starters require a very special design of thyristor firing, voltage measuring and PCB power supply circuitry. Optical fibres should be used completely. Selection and number of thyristors is also to be considered. Every MV soft starter should pass the Partial Discharge Test (EN 50178 part HD625.1). I believe that the best MV soft starters are produced in Israel.

[mrmediumvoltage]

There are several MV softstarter manufactuers in North America who ship globally as well.

Rockwell Automation, Benshaw, Saftronics, etc. All have web site data.

[jraef]

Add Motortronics to the list, which is also brand labeled by ABB, GE, Siemens, Schneider and Toshiba. It is a hot market right now.

Better thyristor designs and higher production volume have allowed cost reductions to the point where MVRVSS starters are now competitive with Autotransformer starters in all but the smallest size (100A and under). Although the product has been around since 1969, it wasn't until this recent economy of scale that they have been taken notice of. Many users are attracted to the concept by observing VFD technology, but are frightened by the extreme costs of MVVFDs. If the engineers become aware of MVRVSS starters as an alternative, albeit fixed speed, they try to find ways to fit them into operating schemes because they are typically 1/8th to 1/10th the cost of an equivalent VFD. Many large scale water projects are now using one or two MVVFDs backed up by several MVRVSS starters as a way of stretching the budget.

For what it's worth, Saftronics has backed off on Medium Voltage starters. They were brand labeling a product made by a small company in Los Angeles that apparently did little testing and had a lot of costly problems in the field.

[GGOSS]

Other potential suppiers include Solcon (out of Israel) and a couple of manufacturers in Italy whos company names escape me right now, but I will post them when they come to mind.

Until recently Solcon were brand labelling for ABB & Siemens however those relationships appear to have disolved for whatever reason.

Those manufacturers best recognised on the global market (in no particular order) are Motortronics, Benshaw and Rockwell. These products are distribued by numerous suppliers globally either under the OEM brand or a brand labelled version thereof.

In addition I am aware of one or two manufacturers (who have traditionally specialised in the low voltage market) that are moving to develop an MV range of products for near future release. Names will of-course be provided when they are ready to go to market.

Regards,
GGOSS

[Damjan]

I have some experience with MV soft starters. I appreciate very much the feature to be able to do all tests and checks of the control equipment, seettings of parameters and similar with a low voltage 400 VAC motor. Only after that the MV is applied and the drive put in operation.

[GGOSS]

Hi All

The company name for the Italian manufacturer of MV soft starters mentioned in my post of 17/3/03 is EEI (Equipaggiamenti Elettronici Industriali S.r.l.). However as they are no longer showing MV products on their web site I am unable to comment as to their present and future plans with such products.

Anyone interested in pursuing this further should feel free to contact EEI directly. Contact details (phone/fax/email etc) are available via the EEI web site.

http://www.eei.it

Regards,
GGOSS

[Igneous]

www.triolcorp.com - the best russian MV Softstarters. AC-15 series...

[jraef]

Interesting, but this is off topic. They do not make MV sodft starters.

[Igneous]

This is not off topic! They (TRIOL corp.) do really MV softstarters! 6-13 kV!!! May be they not lay out an info on english? I found russian page only HERE. One more russian MV softstarters creator is VNIIR READ MORE , READ INFOthey create softstarters for induction motors and synchronous motors (project) (they plan 2 use the variable frequency start )

[jraef]

I'll need to brush up on my Cyrillic then!

[jraef]

I have noticed that some manufacurers of MV soft starters require line or load reactors be installed in the circuit at 4160V and up, or when long lead lengths or high available fault currents are present. Their technical information is lacking in details as to why. I understand this issue with regards to PWM VFDs but I would love to hear from anyone who had to deal with this situation on RVSS starters. If so, was a real explanation given?

[marke]

Hello jraef

I have also seen these referred to in a number of documents/manuals, and llikewise, I have not seen a good explanation for this.
My understanding is that the line reactors are added in some installations to reduce the rate of rise of current through the SCRs when the load has a capacitive element. It would apear that the cable capacitance for a long cable is of particular concern.
When we go from a low voltage (400V) installation to a medium voltage installation (> 10 x voltage) we have a much more significant charging current to charge the spurious capacitance of the circuit. At low voltage, this is not significant, but at medium voltage, this can become significant. If the rate of rise of current, and energy is too high, the SCRs can be damaged.
I would not personally be prepared to quantify these values at this time.

Best regards,

[jraef]

Thanks Marke. I think so too.

Just FYI, I also found this paper that was presented by an IEEE member at the Power Systems World Conference in Chicago IL on Oct. 31, 2002. Wow is it ever filled with good info regarding MV SCR power switching!

http://www.enerpro-i...lt/scrsfire.pdf

[GGOSS]

Hello jraef,

I've just completed reading the first one and a half pages and my head hurts! That normally means one of two things;

a. it contains quality information
b. it contains a lot of bs (no disrespect to the author, I'm just making a joke)

Will comment further once I've finished reading the remaining 11.5 pages ie sometime around January 2004.

Regards,
GGOSS

[marke]

I believe that AuCom are able to supply MV also, see http://www.aucom.co.nz

Best regards,

[schow]

There is another new company producing soft starter now, see http://www.neuronmicrosystems.com

Not sure if they make MV soft starter. I heard their LV soft starter are sold at very low price, for 7.5kW (c/w built-in by-pass) sell for only about USD80.

In fact, can anyone tell me if external by-pass contactor a MUST in a soft-starter controlled system? For instance, fan & pump or compressor applications?

[jraef]

A bypass contactor requirement stems from the packaging of the unit. SCRs are not perfect conductors so they give off about 1.5W of heat per amp of current running through them. If you are opnly talking about a 2 phase unit like that rated at 15A, you are only dealing with at worst 45W of heat. In most cases you could safely put that in a box and not worry too much about over heating. But as the load gets larger, the heat problem gets worse and eventaull it becomes less expensive to add a bypass contactor rather than keep increasing the enclosure surface area to try and dissipate it.

If you are comfortable with using a vented enclosure, you probably don't need a bypass contactor, but keep in mind that with cooling air comes dust, moisture and corrosive contaminants.

Edit: Since this is the Medium Voltage forum I should add that the heat loss is PER SCR, so in MV systems where SCRs are in series strings, the watts loss is even greater. Bypass contactors are ALWAYS included in MV RVSS starters now.

[MaVericK]

Hi all,

There is a company in India (Pune to be precise) which also manufactures MV Soft starters. However, these starters do not use thyristor switching, instead they work on FCMA principle (Flux Compensated Magnetic Amplifier). The technology may sound obsolete, but I can assure you that there are many takers of such starters in India. And if I am not mistaken, they have recently supplied these starters as far away as Jamaica. Link to their site is given below. In India, they have acquired a good share of the MV soft starter market as their price is 1/3rd of an equivalent thyristorized soft starter.

FCMA