Variable frequency drive question

[graffian]

I guess different RFCs make differing amounts of noise. I have a 7.5 (5kw) RFC and it's not very noisy at all.

When I was first playing around with capacitor sizing and ways to switch capacitors, I had an old iron framed motor as the idler and it was really quiet, not much more noise than a motor freewheeling. When I got my present idler it was a lot louder. It was still not really noisy, maybe about the same as volume as the pillar drill. But the motor has to be suspended off the floor and not touching anything, I had ideas of suspending it on rubber bands[exhaust rubbers] but that idea got as far as sticking some old plasterzote, of old bike seat units, under it. it's to to bad on the foam but it climbs off and makes a noise. So if yours is really to noisy you could try isolating the idler.

 

[Shox Dr]

Like I said I don't think mine is loud but then I haven't got another to make a comparison with.

I've just moved mine on to a shelf above my lathe, and also added some more outlets to it, while inside I did notice the motor is isolated with what looks like conveyor belt, crudley trapped between the motor and the chassis case and a M8 bolt though the middle. Hardly isolated, and this is a well know make

So I'm either going to fit some proper rubber dampers or springs

 

[Engineer]

I have a quite old rotary based on a 15hp idler motor, cost £160 from Ebay, and should still be running for many years to come, and if there are any problems, parts required are very cheap and easy to replace. It doesnt make much noise, and power consumption seems to be reasonable.

 

[hareng]

Ronan, no way would that run the Master on two counts.
Its only 220V 3ph output and your motor is 3.75Kw.

No way out unless happen to drop lucky s/h one of these as a minimum on that certain site 380286772351 Plug and play jobby. Know of a 5hp coming up 1 1/4hrs use but that wouldnt do a 3hp unless wired direct to motor!
Even better what i had to have after buying two lesser models wasting £900 is this 380286772352

Other option is change motor to a dual voltage but then still require an inverter with 220V output 3ph cheaper than above http://www.drivesdirect.co.uk/Products/Motor_Inverter_Packages.htm

 

[ronan]

I don't mind wiring direct to the motor hareng , i would have preferred to drive the entire machine but at this stage i just want to make some swarf, the motor is a dual voltage unit and is 5hp , 5hp seems to be as big as the single phase inverters go , would the 5.5 hp inverter have the guts to drive the motor directly ?

 

[hareng]

Simple answer no a 5.5hp wont do it it long term. I had one on a 3hp motor used plug and play lasted 1 1/4hrs, thankyou £650 down the drain! The startup current way exceeded the max the inverter could cope with 150%. Meaning the startup current was like starting a 9hp motor.

Know someone who has a Master using a static convertor and uses the coolant

The inverters usually stop around 3hp 2.2kw single 240 to 3ph 220V.
Might drop lucky on a 5.5kw 7.5hp rotary convertor but expect them well in excess of £250.

Unless you change the motor you need 400v outputs, start looking for a rotary convertor 7.5hp (5.5kw) min or a 10hp.

 

[Engineer]

I don't mind wiring direct to the motor hareng , i would have preferred to drive the entire machine but at this stage i just want to make some swarf, the motor is a dual voltage unit and is 5hp , 5hp seems to be as big as the single phase inverters go , would the 5.5 hp inverter have the guts to drive the motor directly ?

If you can read a drawing and do basic wiring, then why not buy some plans and make an RFC of the size required? Depending on how much you can get an idler motor for, this option will be far cheaper than any RFD, and will be much more reliable.

 

[hareng]

Forgot, having gone through a similar thing i would say no to the 5.5hp wired direct.
A 3hp motor using 5.5hp 400v inverter i could get to easily slow down in short space of usage it got. It tries to correct but aint got the grunt in the real world.
Having gone on to the 7.5kw (10hp) i can get the lathe to slow 6mm cuts but quickly rectifies itself drawing more current at the rate of £1.96 and hour

Not very good realistically i could take 1" off on traverse with 1 1/2hp 240V single phase British from a 13A plug!

 

[ronan]

If you can read a drawing and do basic wiring, then why not buy some plans and make an RFC of the size required? Depending on how much you can get an idler motor for, this option will be far cheaper than any RFD, and will be much more reliable.

A rotary phase converter Seems to be the only option at this stage , its sickening to have the colchester sitting idle when i need the use of it , i have a fair few friends who might have motors sitting under benches so i'll ring around and see what i can get.
Thanks engineer and hareng.

 

[graffian]

A rotary is really simple to make. I haven't seen the plans you can buy
but haven't heard they are any better than the basic 'fitch williams' styleee
converter; should find plenty about them on the net.

 

[Shox Dr]

I was going to build one, but I picked a 7.5HP Transwave for 100quid.

Here are the links to the stuff I found on building your own, not sure who useful they all are it's some time since I looked at them

http://www.practicalmachinist.com/v...se-converter-designs-plans-101231/index5.html


http://www.chudov.com/projects/Phase-Converter/



http://www.metalwebnews.com/howto/ph-conv/ph-conv.html

http://www.metalwebnews.com/howto/phase-converter/phase-converter.html