VFD question - Page 2 - Electrician Talk - Professional Electrical Contractors Forum

yindavies · 09-25-2009, 01:24 PM

Go for an ABB acs800 75KW. They dont do a 55kw anymore. They pack the 75KW into the 55 frame size. I have just been quoted an unbelievable price for one.

At 75kw the line reactor comes with it.

They will also get massive energy savings if you are controlling centrifugal pumps. ABB have patented DTC which gives very accurate control if you require it.

I have just installed schneider 75kw as a freebee. Line reactor is separate.Its a hell of a lump. Not powered it up yet though i will let you know how easy it is to configure.

Lone Crapshooter · 09-25-2009, 08:18 PM

The VFD would be a good idea however a regular motor will not last on a VFD . A VFD rated motor is designed to tolerate the spiked and high yoltages that a VFD puts out. It is not uncommon for a 480 volt drive to put out 800 + volts. Anouther thing is the distance between the VFD and the motor If it is 100+ feet the wire insulation between the drive and motor become a issue. It is not a plug and play type situation.
LC

InControl · 09-25-2009, 09:24 PM

Quote:

Originally Posted by lukejenson

Even tho it says KSB on the nameplate, it looks like a lenze nameplate to me.

Its the European standard for nameplates. They all look the same.

yindavies · 09-26-2009, 12:04 AM

I agree about the old motors not being invertor rated. Can you purchase new high efficiency motors. If you run these pumps on pressure control as stated the payback is huge.

KSB are a pumps manufacturer. They will tell you if the motor is rated for the job.

I would only be concerned if the motor is over 100m from the drive. You can fit a du/dvt filter if longer.

acdrive · 11-02-2009, 02:18 AM

Quote:

Originally Posted by browningwgm

Hello,

A little background on myself. I'm an active duty HVAC tech serving in USAF. I'm currently deployed to a location in Southwest Asia. I have been asked to look at an issue with a water distribution system. They have 8 45KW (60HP) pumps that are delta wound running 415 VAC 3 ph 50hz. There's 6 power leads going to the motor.

Motor data plate states
400 Delta 50hz
690 Wye 50hz

460 delta 60hz

What I want to know is, can this motor be ran off a VFD? The current setup uses 3 contactors. At startup, the start and shorting contactors pull in. After a couple seconds, the shorting contactor drops out and at the same time the run contactor will pull in. This seems to be a pretty standard start sequence that I've seen on some larger chiller units before.

My goal is to run these pumps off a VFD to avoid constant start/stops that's occuring and wearing out our equipment.

If you need more info, please let me know and I can get it. Any help would be appreciated. Thanks.

run off? sorry. I don't understand.

Motor soft starter may be a choice

yindavies · 11-02-2009, 04:19 PM

Hi. I am not sure what the shorting contacting is doing. But because you have 6 leads going to the motor I will assume you are using a star/delta starting method.

You can run most 3 phase motors with a VFD but if they are not invertor rated they could fail after a period with insulation breakdown or bearing failure. When ever possible I will fit a new motor with a non drive end insulated bearing. All depends on the application and wether you can afford the motor failure. Another thing is cable lengths and harmonics. Dont want to put you off but you need to be aware of these if you put allot of VFD,s on a network. These are small motors and I will assume cable lengths of less than 100m so you should be ok. Pay particular attention to earthing the motor and VFD.

I would not look at a soft start unless the customer demands one. When you have a VFD installed it is so flexible. You can run half speed, pressure control, level control basically its up to you how you control the water system. I would like to know what it is though as I may be able to offer more advise.

Basically disconnect the shorting and run contactor and connect the out going start contactor cables directly to the power VFD input and then VFD output directly to the motor. Connect the motor in delta at the motor. Now when start contactor energises it will put juice onto the VFD. You can either configure the VFD to run on start up or use a separate run relay. Like I said not sure what your application is. But using a VFD you can put a very slow ramp rate to protect equipment if so desired.

Try to use the VFD start interlock and connect it to an early break contact on the motor local isolator. This is good practise. Stops should not have changed as you have not altered the original start stop circuit.

Hope this helps.