Rotary Phase Converter (Create 3-phase power from a single phase source)

[nhengineer]

Hi, Forgot to mention, ALL three phase motors here are 240 volts per leg.
Rob.

Here (USA) most 3-phase motors are multi-voltage. That is, 208/240-480. In Canada they do strange things (electrically and political) so I haven't researched that with any diligence yet (120/208 V / 240 V / 480 V / 347/600 V I'm told). I'm still trying to figure out why they insist everyone speak Frenglish (Canadian French) as well as English but not Inuit but that's probably OT.

[old kodger]

Hi David,
I'm reluctant to further confuse the issue, but your comments about multi voltage requires further clarification, and I refer to Aus of course
Unless a motor is dedicated star, OR delta ( in which case they would have three field coils). In configurable motors, those that can be wired star or delta the three coils are center tapped, thereby the motor can be three phase 240volts per phase(star) or 3 phase 415 volts per phase(delta), but the 415 is derived from the angular difference between to adjacent 240volt phases. So we have multi voltages : - 240and 415.
Rob.

[Junker2]

Hum, What nobody seems to want to ask is why you would even need to use the neutral in a 120/240 volt single phase (split phase) system to make a rotary phase converter using a 240 volt three phase motor. Maybe if you have some 120 volt control voltages on the timers and contactors but all you would have to do is get components with 240 volt control voltages. So apparently this design is not very robust. There are easier ways to make a rotary phase converter from a three phase motor, some contactors, some run capacitors, and some timers and or potential relays.

And where do they bond the "ground" to the "neutral" on the secondary side of a transformer bank at the power pole? The only place they normally bond a "grounding electrode conductor" to the "neutral" is at the service entrance.

[nhengineer]

Hum, What nobody seems to want to ask is why you would even need to use the neutral in a 120/240 volt single phase (split phase) system to make a rotary phase converter using a 240 volt three phase motor. Maybe if you have some 120 volt control voltages on the timers and contactors but all you would have to do is get components with 240 volt control voltages. So apparently this design is not very robust. There are easier ways to make a rotary phase converter from a three phase motor, some contactors, some run capacitors, and some timers and or potential relays.

And where do they bond the "ground" to the "neutral" on the secondary side of a transformer bank at the power pole? The only place they normally bond a "grounding electrode conductor" to the "neutral" is at the service entrance.

Thank you for sharing your thoughts, Mr. Junker2.

You have jumped into a conversation without reviewing most of the previous comments. If you had, you would know that we were discussing the difference between Australia's one hot and one neutral/earth ground and the USA's two hots and one neutral/earth ground.

This discussion's only relevance to my rotary phase converter (that you classified as 'not very robust' with zero awareness of how it is configured) is my interest in revising my plans to accommodate a wider geographical area. My design does not require '...some contactors, some run capacitors, and some timers and or potential relays...'. If you'd part with a few dollars and bought my plans, your comments would certainly have more value.

Thank you again.

[old kodger]

Mr Junkers2,
Maybe the answer to the dilemma is for you to design AND BUILD a rotary phase converter so the rest of us can see how good you are.
But make it for a 240volt, one hot line, one ground bonded neutral, designed to run a 240volt star/415volt delta idler motor.

With regard to "where is the supply bonded", it doesn't matter, because even if YOUR local supply is 'unbonded' at your service entrance, it is still bonded at your nextdoor neighbour's property, both sides and all the way down the street.

Regards,
Rob.

[nhengineer]

Mr Junkers2,
Maybe the answer to the dilemma is for you to design AND BUILD a rotary phase converter so the rest of us can see how good you are.
But make it for a 240volt, one hot line, one ground bonded neutral, designed to run a 240volt star/415volt delta idler motor.

With regard to "where is the supply bonded", it doesn't matter, because even if YOUR local supply is 'unbonded' at your service entrance, it is still bonded at your nextdoor neighbour's property, both sides and all the way down the street.

Regards,
Rob.

I wish I'd had the presence of mind to write that. Thanks Mr. Kodger.

[Junker2]

Originally Posted by old kodger

Mr Junkers2,
...............................

With regard to "where is the supply bonded", it doesn't matter, because even if YOUR local supply is 'unbonded' at your service entrance, it is still bonded at your nextdoor neighbour's property, both sides and all the way down the street.

Regards,
Rob.

That is assuming all your neighbors are using the same center tapped 120/240 volt single phase transformer.
I wonder if you can even get the power company to turn your power on without a "grounding electrode" connected to a "grounding electrode conductor" bonded to your "neutral" at your "service entrance".

It's too bad we don't have any other Electrical Engineers or even an electrician familiar with the National Electrical Code to chime in on this conversation. I'm sorry nhengineer. I simply refuse to pay money for an inferior design. However if you sent the plans to me for free I might be willing to review them for a nominal consulting fee.

[nhengineer]

That is assuming all your neighbors are using the same center tapped 120/240 volt single phase transformer.
I wonder if you can even get the power company to turn your power on without a "grounding electrode" connected to a "grounding electrode conductor" bonded to your "neutral" at your "service entrance".

It's too bad we don't have any other Electrical Engineers or even an electrician familiar with the National Electrical Code to chime in on this conversation. I'm sorry nhengineer. I simply refuse to pay money for an inferior design. However if you sent the plans to me for free I might be willing to review them for a nominal consulting fee.

There are two chances of that happening; slim & none.

I'm a bit mystified as to why you think my design to be inferior without even looking at it.

[old kodger]

Mr Junkers2,
I understand that you think that what you say is correct, and in America, it likely IS. However you are either woefully uninformed about Australia, or you just don't listen.
First, GET 120 VOLTS OUT OF YOUR HEAD....IT DOES NOT EXIST HERE! Nor do any motors that use it, Next, it has already been declared and agreed that a transformer would cure the problem, it would have to be 1:2. ie. 240 primary to 480 secondary center tapped. This is not impossible by any means, but here, horrendously expensive
Regards,
Rob.

[Junker2]

Mr old kodger,

Please explain how you intend to connect this 240 primary to 480 secondary center tapped transformer to a 240/415 volt motor. Specifically how do you plan to wire the motor (240 volt delta or 415 volt star)?

Thanks