series/parallel delta performance on a YY motor?

mike_kilroy

Senior Member
Location
United States
As Jraef knows, I posted similar on another forum but did not receive any replies (other than Jraef - thank you!). So thought I would ask here for comments.

I have a rather unique motor nameplate and I would like to double check if my interpretation is correct. This motor/drive combo, sold by mfgr as a matched set, has 3 output contactors (9 contacts total), is used on a dual gearbox machine tool spindle. I am proposing to throw the contactors out and simply run this motor as parallel Y setup to get highest performance over the whole vfd speed range; I think the manufacturer of this motor / drive combo missed the boat in how they applied it, making it much more complex than needed, and gaining nothing in performance.


In the wiring diagram, connector 1, 2, & 3 on motor are phases u,v, & w. each phase is 2 separate windings and they are from A-B & C-D in each connector. In spreadsheet of volts-hertz, contactor 001 means HTC (lo range contacts in - or series D), 100 means HTC (hi range contacts in - or parallel D). Thanks to Jraef, I now know T on nameplate means triangolo for Delta, though the specs (amps) on nameplate do not make sense for that.

I am a little concerned that if my analysis is wrong I will leave a very large aerospace machine unusable and that is not an option! I do not want to give any preconceived notions so will withhold my already written analysis until I hear from others here.


 

Sahib

Senior Member
Location
India
Just a thought: Requisite torque for a particular application(bobbin feeding) at gear box output is produced by series delta and parallel delta winding connections. So not availing those connections and using only YY connections may not produce the required torque through the gear box with VFD.
 

mike_kilroy

Senior Member
Location
United States
Just a thought: Requisite torque for a particular application(bobbin feeding) at gear box output is produced by series delta and parallel delta winding connections. So not availing those connections and using only YY connections may not produce the required torque through the gear box with VFD.
more info plse Sahib.... I am not running YY: I am running delta ony; series and parallel.
 

mike_kilroy

Senior Member
Location
United States
The volts-hz chart attached shows that in series delta the motor, rated 160v in delta, is run 0-400v from 0-50hz so it receives 200v/coil.

The volts-hz chart attached shows that in parallel delta the motor, rated 160v in delta, is run 0-400v from 0-100hz so it receives 200v/coil.

Therefore my conclusion is there is no advantage at all running this motor in series delta, thus the system can be simplified by removing all output contactors and just run parallel delta.
 

Sahib

Senior Member
Location
India
Thanks for your clarification, Roy.

One thing:

How do you want to operate the motor? Do you want to operate the motor continuously in parallel delta configuration? Perhaps the motor is of intermittent duty and the motor manufacturer has put in the series delta configuration to run the motor at no load (no feeding of bobbin) to reduce the motor heating?
 

Sahib

Senior Member
Location
India
Is there any requirement for torque at a particular speed from series delta configuration, because the same requirement may not be met from parallel delta configuration?
 

mike_kilroy

Senior Member
Location
United States
Is there any requirement for torque at a particular speed from series delta configuration, because the same requirement may not be met from parallel delta configuration?
If we put same v/hz curve into the series as parallel, it would be different; ie., if we run 0-200v from 0-50hz then stick at 200v upto 100 hz, the series motor would produce 4x less PEAK torque due to V^2 undervoltage I believe. But they don't: they run 0-400v 0-50hz, then constant hp from 50hz to 100hz.

In parallel delta, they run 0-200v from 0-50hz, then continue upto 400v @ 100hz - so from 0-50hz it produces EXACTLY the same torque at any speed from 0-50hz. From 50-100hz it continues in constant torque rather than constant hp so produces 38kw by 100hz rather than same 18kw of series.

So in application, if they want LESS torque from 50-100hz in low gear, we can do that in the drives internal PLC program.
 

Sahib

Senior Member
Location
India
Then why there is an instruction that at no feeding of bobbin the motor be run at series delta configuration? Is it needed to cool down the motor (perhaps not continuous rated)during any automation purposes?
 
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