Need more HELP with understanding Inverters

[Jaeger_S2k]

The hunt (although more of a drag net) for a 5hp / 4Kw single phase motor continues.
At the same time looking at Inverters, it's quite an economical route. 3 phase motors are much cheaper than single and with the inverter still work out quite reasonable.
But I'm not 'Fully standing under' the 3 phase supply and motor voltage.

This has caused much thinking and have a few questions I can't answer no matter how I search.

What are the options.

What are the standard 3 ph variations in the UK?

Input - 240 v What are the outputs 3ph 240, 3ph 380, 3ph 415v?

Then there's talk of 'if you don't have dual voltage, star and delta (head hurting again) then you'll need and inverter that boosts the voltage to 415v'
So to me that's means, 2 phase motors (that are dual voltage) run 240 or 415, so would a US inverter work on that?

Are there motors that are 3ph 240? Or am I getting confused by the US.

 

[madkayaker]

OK three phase motors are great. They can be wired in STAR and DELTA easy way to remember which is highest torque is "send it the Delta's when things get tough" Some 3ph motors are duel voltage this is what you need to run off standard inverter as a standard inverter is just an electronic switch that switches the 230V @ correct sequance and time for simulated 3ph. There is some inverters that also have a transformer in them to generate true 400V 3ph. Looks on ebay for a company in Nottingham they have been helpful in past with matching motors and inverter or find your local motor rewinders they often have second hand kit.

 

[Luke]

What are the standard 3 ph variations in the UK?

415V, which is 415V phase-to-phase, or 230V phase-to-neutral. This is the only standard. (ahem )

Input - 240 v What are the outputs 3ph 240, 3ph 380, 3ph 415v?

A single phase inverter will only produce 240 three phase. unless there is a seperate transformer as previously mentioned.

Then there's talk of 'if you don't have dual voltage, star and delta

Motors on inverters should be Delta wired. the inverter controls the starting voltage and frequency so you don't get the same inrush current you would with DOL starting of a delta motor. delta wiring also produces more torque than Star

To answer your original question, you will be ok running a 3ph motor from a 1ph inverter, if you find one big enough. alternatively, given the right drive, you can run a 3ph drive from 1ph, using Live for 2 of the 3 phases, and N for the other. you would have to derate the drive as you'll only be using two thirds of the rectifying circuit. and obviously you'd derate the drive to 230v 3ph still.

 

[piman]

Hello Jaeger,

to expand on MK's explanation.

Many U.K motors are wound for 415 Delta, that is each phase winding requires 415 volts so applying 220 volts as many inverters give (220\127v) is under powering the motor and it will overheat. Some motors are wound so that the phase winding is 220v so to run one of these on the normal U.K. 415 v supply it must be connected in star, which gives a reduced voltage on each phase winding by a factor of 1.734 as the voltage is split over two phase windings.
If that is as clear as mud, just look at this for a diagram of both star and delta connections which hopefully will help to make it clear? :-

http://www.woodsbas.demon.co.uk/calcs/stod.htm

Alec

 

[rtbcomp]

A single phase inverter will only produce 240 three phase. unless there is a seperate transformer as previously mentioned

Phase to Phase or Phase to neutral?

 

[madkayaker]

most inverters will not supply N

 

[piman]

Hello Luke,

"you can run a 3ph drive from 1ph, using Live for 2 of the 3 phases, and N for the other. you would have to derate the drive as you'll only be using two thirds of the rectifying circuit. and obviously you'd derate the drive to 230v 3ph still."

Can you explain that further as I don't understand how this will work?

Alec

 

[Luke]

Phase to Phase or Phase to neutral?

phase to phase, and i meant 230

 

[Luke]

Hello Luke,

"you can run a 3ph drive from 1ph, using Live for 2 of the 3 phases, and N for the other. you would have to derate the drive as you'll only be using two thirds of the rectifying circuit. and obviously you'd derate the drive to 230v 3ph still."

Can you explain that further as I don't understand how this will work?

Alec

A 1ph drive rectifies L-N once and gets a voltage of 340V ish on the DC bus.

A 3ph drive rectifies L1-L2, L2-L3,L3-L1 and gets a voltage of 600V ish on the DC bus.

The 1ph drive has the capacitance to take out (most of) the rectified ripple.
The 3ph drive normally wouldn't have much ripple to contend with, due to the 120 degree phase seperation.

If you stick 230 on to a 3ph drive, twice, you can still rectifiy L-N and N-L, but not L-L. hence using 2/3 of the rectifying ability of the drive. you also end up with more DC ripple, due to the missing two phases, so the DC bus capacitors have to work much much harder.

 

[Jaeger_S2k]

A 1ph drive rectifies L-N once and gets a voltage of 340V ish on the DC bus.

A 3ph drive rectifies L1-L2, L2-L3,L3-L1 and gets a voltage of 600V ish on the DC bus.

The 1ph drive has the capacitance to take out (most of) the rectified ripple.
The 3ph drive normally wouldn't have much ripple to contend with, due to the 120 degree phase seperation.

If you stick 230 on to a 3ph drive, twice, you can still rectifiy L-N and N-L, but not L-L. hence using 2/3 of the rectifying ability of the drive. you also end up with more DC ripple, due to the missing two phases, so the DC bus capacitors have to work much much harder.

 

[madkayaker]

have you found a potential motor?

 

[Jaeger_S2k]

OK this is going badly (for me).

I know (you'd never know I have my Amateur Radio Licence, but it was a long time ago!) can you explain it as if you were explaining it to .....



her ......

 

[Jaeger_S2k]

have you found a potential motor?

I'm trying to understand what I'm looking for/at first!

 

[madkayaker]

need a inverter and a duel voltage motor

 

[piman]

Hello Luke,

I misunderstood what you were saying, I thought you meant applying 1ph to run a 3ph motor not an inverter.

Alec

 

[Luke]

Alec, sorry, didn't mean to confuse you, or Jaeger!

 

[Jaeger_S2k]

OK So - As I understand it then, a (3ph) dual voltage motor will run on either 240 3ph or 415 3ph?

 

[piman]

Hello Jaeger,

it will probably have something like 220v\400v on the name plate, if it only has 415v it is not what you want unless you do find a 415v inverter?

Yes the dual voltage motors work on either supply, as long as the terminals are reconfigured.

Alec

 

[madkayaker]

that's it


Piman got in way

 

[madkayaker]

a 415V inverter only changes the Hz of a 415V supply