Shadows_Cord

Wanted to get some opinions on one vs. the other. I have a 930kV 3y, and a 1480kV 3.5D at my disposal. I'm curious as to how the 930 would behave in a heavy Muggy. I was planning on running the 1480kV on 5 and 6S power. The 930 on 6S could be interesting with the characteristics of the Wye wind. That would have to run on 6s all the time, and may want more power.
Thoughts?
Thanks,
Cord

Dr_T

Ah,... tough crowd eh?

So you ended up getting both motors? In general D-winds require more current at start-up and because of that Y-winds are a bit more common for cars. Apart from that, the only thing to be aware of when you switch is that the suitable timing advance differs between the two: think I read something like 0-5° for D-wind, and 0-15° for Y-wind.

Whether the 930kv on 6S will work for you basically depends on how tall you can gear (i.e., whether you can gear up to the no-load wheel speed you want). I'll be trying a 900 kv on 6S with some tall gearing (pinion > spur) myself for a new project. Might be the low-kv high-gearing combo is more prone to cogging... If you have both motors, I'd say try out and see if you can tell the difference between the two, geared for same no-load wheel-speed. Would be interesting to see such a comparison.

Eric Bryant

iTrader: (44)

There is no difference between delta and wye motors of the same basic geometry and Kv with regards to starting current or timing requirements.

Delta motors do suffer from slightly lower efficiency due to recirculation current around the delta.

Some sensorless ESCs will not properly drive some delta motors, so this must also be considered.

Dr_T

Interesting Eric, been looking for good info on that for a while, but all I could find on the net was what I listed before. Do you have some good references for background reading for us on the topic?

Thanks!

DamianW

iTrader: (5)

Delta wound has the applied voltage across one winding where as wye wound the applied voltage is across 2 windings at any given time.

In industrial applications some motors can be configured to be wye or delta often combined with controllers to switch the configuration whilst the motor is running. IE they use wye to start the motor with reduced starting current then switch on the fly to delta wound for maximum power.

A little rusty (I haven't done this for 8 years) but the number of turns changes by approximately square_root(3) or 1.73 for the same motor delta or wye wound.

Most of which is irrelevant for RC cars. From what I have seen with an equivalent power motor, delta wound motors are a little smoother which can be important in MOD.

Eric Bryant

iTrader: (44)

I can't immediately think of any good online resources - my knowledge of this subject was obtained by designing and building brushless motors for a number of automotive applications a few years back. We had to experiment with both wye and delta winds because our motor geometry and winding equipment placed limits on the size wire that could be accommodated in production.

Probably the single biggest issue with delta motors is that some ESCs with less-sophisticated sensorless modes will not play well. Wyes are (relatively) much easier to commutate using 120-degree operation and zero-crossing detection on the open phase.

Eric Bryant

iTrader: (44)

To be technically accurate, applying voltage across one winding of a delta also applies it across the other two, since they are all connected. This is why 180-degree commutation (applying voltage to all three terminals) is almost always used with delta, where as wye works almost as well with 120-degree commutation (applying voltage across two of the three terminals).

That is correct.

There shouldn't be any noticeable difference in torque ripple between the two; delta is technically a bit worse as the circulation current causes a bit of current ripple (and thus torque ripple) in some of the upper-order harmonics (3rd, 6th, and 9th ring a bell). That being said, the ESC behavior with the two different types of motors is going to play a significant role in how the overall system behaves.

Ed Anderson

iTrader: (26)

Delta has more torque. I'd say that's an odd combination. In 34 years of hooking up motors... I've ran into that maybe three times. ... and it was the opposite they started on delta and switched to wye. Only seen that set up on sludge pumps in refineries.

DamianW

iTrader: (5)

The starting current which is 5-6 times full load current requires current limiting or an over sized supply is the issue. VSD or soft starter is the preffered method but in larger systems swapping the winding configuration is not uncommon.

DamianW

iTrader: (5)

I don't think it matters much for rc applications but both winding configurations have harmonics, in power systems delta is preferred as it provides a circulating path for harmonics rather than returning to the supply with a star winding.