Author Topic: Changing the Motor Voltage  (Read 11012 times)

Offline Ivan

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Re: Changing the Motor Voltage
« Reply #15 on: March 07, 2013, 06:17:21 PM »
actually.. it totally makes sense to pick the largest gauge wire you can wind by hand.  largest gauge = highest current = lowest voltage for same HP.  also, by picking just ONE gauge to work with you don't have to buy multiple spools. this works out nicely if you get near 100% slot fill  but that will depend on HP rating and # of slots.  of course, you could optimize slot fill % by changing wire size .. but hen you have to have multiple wire sizes on hand which is expensive. 

ps. turkey boilers are on sale this weekend, $39!    :)

No same gauge (18)  just change number of wires in-hand to make up the slot fill.  A small wire or a big wire can have the same gauge (strands) just more or less strands for diff amp loads.
:co<:  If you bought just one or two extra can goods a week and donated to a food bank   Nobody would go hungry.

Offline smtv

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Re: Changing the Motor Voltage
« Reply #16 on: May 25, 2013, 03:06:21 PM »
this just screams excel sheet :)

Well  HighHopes, you build it, and post it,  lets see how it works out.

Ivan

Hi, everyone! I'm T.V., from Brazil.
I've created a Google Spreadsheet to do the math (as HighHopes suggested), according to the example Ivan showed.
You may download it, or even use it on line.
Hope you enjoy.

https://docs.google.com/spreadsheet/ccc?key=0ArourR-LABPFdFVUM1pYcEpDY0htVkVaZUlpN3lMQXc&usp=sharing

Offline mizlplix

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Re: Changing the Motor Voltage
« Reply #17 on: May 25, 2013, 05:22:36 PM »
WOW!  Really nice, SMTV.  Thanks, I am sure it will get used and added to.

Miz
1930 Ford Speedster, AC50, full manual powerglide, 6.14gears, 38-130AH CALBs.

Offline maddkraut03

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Re: Changing the Motor Voltage
« Reply #18 on: September 15, 2013, 06:47:26 PM »
Can you explain Dual layer winding?    Im not clear on that thanks

Offline Ivan

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Re: Changing the Motor Voltage
« Reply #19 on: September 16, 2013, 06:48:18 AM »
Can you explain Dual layer winding?    Im not clear on that thanks

Dual layer,  means there will be two phases laied in each slot.

ok if ya got a 36 slot stator, you would have 72 half slots.

one phase: 
3 coils per pole = six sides  times 4 poles  =  24 half slots per phase on the slot fill.  So it takes two phases to fill a slot.  Dual layer.

So: each phase takes 24 half  slots  times 3 phases = 72.
:co<:  If you bought just one or two extra can goods a week and donated to a food bank   Nobody would go hungry.

Offline HighHopes

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Delta vs. Wye wound
« Reply #20 on: November 12, 2013, 05:00:59 PM »
i'm wondering about the calculations given in the first couple of posts in this thread, if they need to be modified somehow if the original motor is WYE wound but the new re-wound motor is DELTA wound? 

for example, let's say our design was to NOT change the voltage, just start with WYE motor and then re-wind for DELTA with the same line-to-line voltage.  note it is a common misconception that delta wound motors have lower line-to-line voltage... they don't, they require the same DC bus voltage and the inverter supplies the motor with the same phase voltage.  but the current in a delta wound motor is higher and the torque generated is higher at low rpm (which is probably why they are preferred for EV application).  so i guess i am wondering about the circular mills calculation?

Offline mizlplix

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Re: Changing the Motor Voltage
« Reply #21 on: November 12, 2013, 05:05:44 PM »
The circular mills calculation is based solely on the size of the stator slots. 
No change there.

Wye to delta only affects the wire strand length, thereby the voltage and torque.

Miz

Go get him Ivan....LOL
1930 Ford Speedster, AC50, full manual powerglide, 6.14gears, 38-130AH CALBs.

Offline Ivan

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Re: Delta vs. Wye wound
« Reply #22 on: November 12, 2013, 05:37:55 PM »
i'm wondering about the calculations given in the first couple of posts in this thread, if they need to be modified somehow if the original motor is WYE wound but the new re-wound motor is DELTA wound? 

for example, let's say our design was to NOT change the voltage, just start with WYE motor and then re-wind for DELTA with the same line-to-line voltage.  note it is a common misconception that delta wound motors have lower line-to-line voltage... they don't, they require the same DC bus voltage and the inverter supplies the motor with the same phase voltage.  but the current in a delta wound motor is higher and the torque generated is higher at low rpm (which is probably why they are preferred for EV application).  so i guess i am wondering about the circular mills calculation?

First of all, you don't wind for delta or wye.

The cir/mills has nothing to do with delta or wye, its just for slot fill.

Delta and wye is the connections.

Connecting in wye would double the winding voltage and half the torque.  Thats why we figure the turns for the winding voltage.
ie Curtis controller,  Delta connection. 
:co<:  If you bought just one or two extra can goods a week and donated to a food bank   Nobody would go hungry.

Offline HighHopes

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Re: Changing the Motor Voltage
« Reply #23 on: November 12, 2013, 06:45:10 PM »
i was thinking the circular mills  was related to cable ampacity, but you are saying the cicular mills calculation is to make sure the slot gets filled.  OK, got it :)

i suppose the ampacity sort of works itself out because we chose the largest gauge wire we can wind with by hand (#18) and then the motor/slots are only so big it self limits to the cooling capability of the motor anyway.  that is, if the slots were bigger/deeper/longer perhaps we could fit more copper and ampacity would increase.. but so too would the physical size of the motor.  in reality, the size of the motor & slots is fixed, so the power is fixed, we just fill the slots with copper as they exist, but in such a way in accordance with your math & instruction (to get lower voltage & higher current operation).

ps, the reason i was asking is because i am wondering what the current rating needs to be for the MOSFET inside my DIY controller.   its funny, the blocking voltage rating of the mosfet is the same no matter how the motor is connected becasue the DC bus voltage will not change, only the current rating.  so, theoretically, for delta connected motor, the voltage rating is the same but the current rating is higher which of course costs more $.. but you get more torque so.. now we see how it is not free.  nothing is for free in engineering, always a trade off!

just an update, to be more clear.. i am interested in determining the phase current in the cable feeding the motor, not the phase current in the motor winding (i think i was getting confused myself!).    so following ivan's motor rewind instructions, we rewind to get lower voltage (higher current), same power.  then we connect the windings in Delta.  done.    the impact on the controller is now the rated current of the mosfet must be higher: 
Iphase_cable = sqrt(3)*Iphase_motor_delta.

Offline Ivan

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Re: Changing the Motor Voltage
« Reply #24 on: November 13, 2013, 04:30:27 AM »
Highhopes 

Lets look at some basic numbers on a controller, motor.

It seems most ev cars need about 60-80 amps current to hold a speed of 50-70 mph, depending acourse on weight.

So I would want a controller that was able to maintain atleast 150=200 continuios amps.

With that said, your motor would need to handle (the winding) the same current.

This is one of the reasons a stock, off the shelf motor will not work for ev use.

That is where the inhand count comes into play. Think of inhand as a bigger wire, 4 gauge to 1/0.  1/0 can handle more current.

So if we need 150-200 continuios amps to maintain a certain speed we would need 4 times that for a decent exceleration.

So if we look at just this problem of high currents, size of motor slots, we are allmost forced to reduce the voltage of the winding so we can gain higher currents.

 As we allready know, higher current equals more torque.

:co<:  If you bought just one or two extra can goods a week and donated to a food bank   Nobody would go hungry.

Offline HighHopes

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Re: Changing the Motor Voltage
« Reply #25 on: November 13, 2013, 07:42:32 PM »
if you rewind for 100V line-to-line, and ask for phase measurement of 150A to 200A, what you are really saying is that for decent acceleration you need 20HP induction motor in light weight vehicle.  this configuration would also require a 172VDC battery pack capable of delivering 100A continuous.  can a curtis do that?

Offline Ivan

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Re: Changing the Motor Voltage
« Reply #26 on: November 14, 2013, 12:35:11 AM »
if you rewind for 100V line-to-line, and ask for phase measurement of 150A to 200A, what you are really saying is that for decent acceleration you need 20HP induction motor in light weight vehicle.  this configuration would also require a 172VDC battery pack capable of delivering 100A continuous.  can a curtis do that?

No on the 20hp.  A whole other subject.

Don,t no where you come up with the 172v batt pack.


A 100V wind is to high a voltage, when I wound a 3 turn motor for Mizs car we had to do 8 inhand at 3 turns and it would not take the current (smoked it).

So what did we learn from that. 

We know we need high amps for torque and to maintain speed, right..

Stop with all the numbers, this is simple physics.

Here is something to think about.

Think of one  motor slot, there is two different things we can do with this slot.

We can add wire for current or voltage but not both.

:co<:  If you bought just one or two extra can goods a week and donated to a food bank   Nobody would go hungry.

Offline HighHopes

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Re: Changing the Motor Voltage
« Reply #27 on: November 14, 2013, 03:45:09 PM »
thanks for the reply(s). 

the 172V comes from a discussion with mizlplex, i just asked him what his ideal controller would be rated for.  i assumed he was thinking of using that "ideal" controller on his existing car & rewound motor.

i'm not trying to figure out if how to improve your methods or how to add math to your methods, i just believe you on faith you know what you're talking about and i'm perfectly willing to give it a go exactly as you describe.  my #s questions come from me trying to figure out what the ratings needs to be for my DIY controller, that's all. 

my original post, perhaps should have been reworded like this:
let's say i have already purchased a 10HP motor and i use your methods to rewind the motor.  what voltage should i pick as target voltage?  after that i can determine what my phase current nominal will be because i assume i still have 10HP rating after rewind.   I'm not worried if there is a controller out there somewhere in the world that can handle your selected line-to-line voltage & phase current because i will design my own to match exactly the needs of the project.  i just don't know what those needs are, so am trying to figure that out.

ps. i am aware that curtis has spend a great deal of $ & time developing their very successful product.  i don't mind recreating the wheel because it is fun for me and also i have other aspirations for such a controller that for sure curtis can not do which will become important to me at a future date.  so it will be good if i have a first working prototype to build off of.  that first working prototype (assuming it is successful) will be documented on this forumn .. again, just for fun. 

Offline mizlplix

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Re: Changing the Motor Voltage
« Reply #28 on: November 15, 2013, 12:10:31 AM »
Look at it this way:

A stator slot needs completely filled no matter what.

There are two ways to fill it:
1-A small in hand bundle and many turns.
2-A large in hand bundle and a couple of turns.

Way #1 is a low current/high voltage type. The Curtis controllers can
not supply over 70 volts, so this is not going to work with them.
It WILL work with maybe a Rinehardt or a Sevcon controller.
It usually uses small diameter wire.

Way#2 is a lower voltage/ high current type, which IS necessary
when using a Curtis type controller. It usually uses a large wire diameter.

The smaller wire diameter will give a better slot fill due to the better
stacking ability of the wire and I guess you could do a type #2 high
current wind with small wire, but it would be a lot more time
consuming to do so. (After all, a welding cable is made of small wires)
Plus I do not know if the advantage of the better slot fill would
be worth it.

It surely would be a good thing to try as an experiment now
that there is a dyno and Ivan is not working on his truck anyways.

Miz

1930 Ford Speedster, AC50, full manual powerglide, 6.14gears, 38-130AH CALBs.

Offline Guillermo

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Re: Changing the Motor Voltage
« Reply #29 on: May 15, 2014, 07:04:19 PM »


Hello Friends ..!

Im Guillermo Iturriaga from Chile. I have followed with great attention the adventures of converting a vehicle to electric and more attention with the re design a three phase motor and made ​​to operate at lower voltages.

As good engineer remains very intrigued and I began to investigate I could do to achieve full induction motor efficient and powerful .

I've never winding an electric motor , but if I 'm designing induction electric motors with a program of Russian physical brilliant.

I can model an induction motor with 99 % accuracy , since all behavior simulates a real one.

so selflessly offer my help to do a better electric induction motor . I 'm working on designing an engine with aluminum frame and rotor copper , based on one of 18.5 kw. which will take away the aluminum rotor and replace it by one of copper. This when you can buy one in China. hehehehehhe ....

I am dedicated primarily to design and manufacture VFD for electrical induction motors for various clients.

I have designed a VFD for my electric motor , that would promote a Chevy Cavalier 99 with Pb- acid batteries , deep cycle .

My big dream is to make my own electric car Low cost but very efficient .

Ivan Thanks for adding me to your club , I hope to be a contribution to the community.

Best regards .