[vrsi367]

Hello community,

I've found a couple of posts online selling two industrial motors near where I live, 10HP and 15HP both are 3600 rpm. If I understand correctly the power is enough to use in a small car re-using the manual gearbox to maximize the torque at different speeds, but apart from that I have no clue where to start with the conversion using those kind of motors.

A few questions to see if I can start wrapping my head around the technicalities of these kind of conversions.

¿Do the battery bank need to be 220V DC or can it be 108V or even less for those motors? I would prefer no to have to rewind them.

Follow up question, sort of, ¿what kind of equipment would allow to convert DC voltage to the 3-phase AC voltage needed for the motors, and also would allow for controlling the rotation speed and direction?

¿Can that kind those kind of motors be used as a generators when the vehicle is decelerating, if so what kind of equipment would be needed to enable that functionality?

I have a background in electronics engineering but I'm a bit rusty, and would need to undust my notes to see what can I do to complete the task.

Any help or comment is very much appreciated.

 

[cricketo]

All the magic is in the motor controller (inverter). It will have an allowable input voltage range, and allowable output range for the motor. So you start by finding one that will be able to put out what you need for the motor, and then see what it can do on the DC side to decide on the battery pack voltage.

 

[vrsi367]

All the magic is in the motor controller (inverter). It will have an allowable input voltage range, and allowable output range for the motor. So you start by finding one that will be able to put out what you need for the motor, and then see what it can do on the DC side to decide on the battery pack voltage.

Thanks a lot.

 

[Jordan325ic]

Do you have any idea of the size and weight of these motors? Quite often industrial motors are far too large and heavy for a given power output to be considered for EV applications.

 

[vrsi367]

Do you have any idea of the size and weight of these motors? Quite often industrial motors are far too large and heavy for a given power output to be considered for EV applications.

You are right, the one with 10HP output seems about 167 lbs, it's like about 45% heavier than some motors I've seen in some conversion kits, besides its only 10HP.

The price is about $180 each motor though, so perhaps if I could find a controller that I could reuse later with a proper EV motor it might worth a try, although I'm not entirely sure.

 

[Jordan325ic]

You are right, the one with 10HP output seems about 167 lbs, it's like about 45% heavier than some motors I've seen in some conversion kits, besides its only 10HP.

The price is about $180 each motor though, so perhaps if I could find a controller that I could reuse later with a proper EV motor it might worth a try, although I'm not entirely sure.

I mean, you can find 10hp continuous motors designed for EVs that come in at less than 40lbs.

Aside from the controller, you're also going to be doing custom motor mounts, figuring out how to hook it up to the driveshaft or transmission and getting all the packaging right. All needing to be redone when you switch to a more capable motor. Even if you can get industrial induction motors totally free, it would still be worth it to start with a motor designed for traction applications rather than starting with a huge industrial motor. Unless this is some sort of budget-challenge '$2000 EV!".

 

[vrsi367]

... Even if you can get industrial induction motors totally free, it would still be worth it to start with a motor designed for traction applications rather than starting with a huge industrial motor.

I totally see your point.

Unless this is some sort of budget-challenge '$2000 EV!".

It is sort of a budget-challenge, EV conversions in the country where I live, Venezuela, are like 20 years behind the rest of the world. Even the neighboring country, Colombia, has some nice conversions that are already more than 10 years old. The problem in Venezuela was that gasoline was practically free, and EV conversions never had a chance to develop in the country. Now the current situation screams for the need of EV, but most people can't afford even a cheap conversion kit let alone a new EV. So, I've been talking with my brother to see if we can come up with something that could be done for people in Venezuela with $1000 or less excluding the battery pack.

 

[cricketo]

I totally see your point.



It is sort of a budget-challenge, EV conversions in the country where I live, Venezuela, are like 20 years behind the rest of the world. Even the neighboring country, Colombia, has some nice conversions that are already more than 10 years old. The problem in Venezuela was that gasoline was practically free, and EV conversions never had a chance to develop in the country. Now the current situation screams for the need of EV, but most people can't afford even a cheap conversion kit let alone a new EV. So, I've been talking with my brother to see if we can come up with something that could be done for people in Venezuela with $1000 or less excluding the battery pack.

What about motors from industrial machinery ? Forklifts, boom lifts, etc ?

 

[vrsi367]

What about motors from industrial machinery ? Forklifts, boom lifts, etc ?

Thanks for your suggestion. I'm going to look for those too. I made a quick search and it seems most of those that are sold online here where I live are propane or diesel powered, but if I can find one with an electric motor that I can use I'll report back.

 

[brian_]

I've found a couple of posts online selling two industrial motors near where I live, 10HP and 15HP both are 3600 rpm.

The rated speed will be what they run at with 60 Hz AC power; they will run faster or slower by changing the frequency of the supplied power, which is what a controller/inverter does. The rated power is at the rated speed and is likely what they can handle continuously. In a car, they could probably be run faster and run much harder in brief bursts.

However....

Do the battery bank need to be 220V DC or can it be 108V or even less for those motors? I would prefer no to have to rewind them.

Assuming they're three-phase, if you check the specs you'll likely find that they are wound for 480 V... and that's a root-mean-square voltage, so the DC voltage needed to deliver that is much higher. Variations of industrial motors made for EV use are wound for much lower voltage.

Follow up question, sort of, ¿what kind of equipment would allow to convert DC voltage to the 3-phase AC voltage needed for the motors, and also would allow for controlling the rotation speed and direction?

That's what the controller/inverter does. In a car, you normally don't try to control the speed - you control the torque, and the controller follows the motor speed.

¿Can that kind those kind of motors be used as a generators when the vehicle is decelerating, if so what kind of equipment would be needed to enable that functionality?

Yes, if these are any common type of three-phase motor (likely induction) they can act as a generator so they can provide regenerative braking - it's a normal feature of the controller/inverter.

 

[vrsi367]

@brian_ , thanks so much.

 

[MattsAwesomeStuff]

My forklift motor I think is rated for 17hp continuous, 52hp for 15% duty cycle. It's 250 lbs.

Lots of forklift motors are rated ~15hp and there's guys using them upwards of 400hp in drag races.

Generally I'd say they're not spec'd for any airflow, so, in a car with a fan you'd probably get a lot more out of them.

It's almost a non-issue anyway because if you're using the motor that heavily you'll probably run out of battery before you accumulate enough temperature rise.

I'd say it would probably work fine, and if it's free and you're interested then go ahead, but it's probably not a good way to go.

Probably the cheapest and easiest way to convert is to take a 2nd or 3rd generation Prius transaxle and inverter ($150 + $150 at most at a junkyard, often can get them for $50 total), and then use the swap-out control board from OpenInverter.org (2nd gen) or EVBMW.com (3rd gen). That gives you bulletproof engineering for dollarstore prices.

 

[brian_]

My forklift motor I think is rated for 17hp continuous, 52hp for 15% duty cycle. It's 250 lbs.

Lots of forklift motors are rated ~15hp and there's guys using them upwards of 400hp in drag races.
...

I'd say it would probably work fine, and if it's free and you're interested then go ahead, but it's probably not a good way to go.

Sure, and to get that higher power you supply higher voltage. If they're brushed DC motors from forklifts rated for 36 volts DC, that's easy. If they're actually 3-phase industrial AC motors (as described in the title) all you have to do with these lumps is provide the inverter with a couple thousand volts to get them going usefully.

Matt, did you miss the title, or did you assume that these are low-voltage 3-phase AC motors from something like a newer forklift? Perhaps they are.

 

[rishimaze]

I skimmed through the posts. Hopefully I'm not repeating what was already said too badly!
1. Industrial induction motors are heavy and low power density for the weight and size. However, they last forever so reliability is going to be great.
2. Tesla uses Induction motors and have been for many years. They can be very EV worthy.
3. A 3 phase induction motor designed around 110v per phase or 220v per phase will probably do best at that voltage. Running it at lower voltage is doable, but then you will probably need to raise the amperage in the motor and that will make it run hotter.
4. I don't recommend brushed motors becasue they are not very efficient. There are tons of old fork lifts out there with perfectly good motors in them for cheap...so why not? Most are 48v systems and I think you will do better at more like 100v. The forklift controller is probably ancient tech and replacing it with something new is worth it to get 100v and proper motor control that is recent.
5. Weight is always a concern. Old and cheap (fork lift motor) probably means lots of weight and hugeness.
6. A BLDC motor at probably half the weigh and size will outperform whatever forklift motor you might get and be more efficient too.
7. Just my opinion I suppose, but I'd go with a hybrid car BLDC or PMAC motor and not bother with some other motor technology. Both PMAC and BLDC are the same wind, just different ways to sense armature position. Put halls in a PMAC and now its BLDC. Put a optical wheel in a BLDC and now it's PMAC. Controllers for both of these types of motors are easy to find and abundant.
8. If I found a forklift with a PMAC or BLDC motor in it...that could be a good find. Otherwise, brushed stuff is heavy, poor efficicny and huge. Why would you want that? I guess free or very low cost could make it compelling.
9. You can find used hybrid car motors easily enough and not break the bank. I think all hybrid cars use PMAC or BLDC motors in them and they are abundant and cheap! Some hybrids build the motor into the drive train. Others have it as an add-on and those motors are in their own shell. Buick was making hybrids like that for a while. I think so was Ford. They put a motor on the serpentine belt. That's a great option for DIY project.
10. I bet in your local junk yards you will find hybrid cars that you can grab the motor, inverter and battery for your project.

 

[brian_]

1. Industrial induction motors are heavy and low power density for the weight and size. However, they last forever so reliability is going to be great.

True of anything industrial - motors or otherwise.

2. Tesla uses Induction motors and have been for many years. They can be very EV worthy.

Tesla... and everyone else for a couple of decades, including the limited production vehicles of two decades ago (remember the GM EV-1, Ford Ranger EV, and the docu-fiction "Who Killed the Electric Car?"). Tesla has almost completed their transition away from induction to PM, but induction is still a viable choice - Audi, for instance, has recently chosen to use induction motors.

Although a three-phase industrial motor is most likely induction, whether the motors are induction or not is not really the issue.

3. A 3 phase induction motor designed around 110v per phase or 220v per phase will probably do best at that voltage. Running it at lower voltage is doable, but then you will probably need to raise the amperage in the motor and that will make it run hotter.

AC voltages are root-mean-squared - the peak-to-peak voltage is much higher. And three-phase motors at only 110 V or so (even phase voltage which is line-to-neutral) are unusual. Line-to-line voltage is always 1.732 (square root of 3) times the line-to-neutral (or phase) voltage. Even 120 V (phase) / 208 V (line-to-line), which I think is the lowest available three-phase power in North America and is used in commercial buildings but not much industrially, is 208 VRMS line-to-line, so the inverter would need more than 208 V DC supply. 208 VRMS would be 208*sqrt(2) V peak, or 2*208*sqrt(2) V = 588 V peak-to-peak... so you need a 588 volt battery to feed an inverter to make 120/208 V 3-phase power.

So... 588 VDC to match the rated performance, and higher voltage to be useful.

7. Just my opinion I suppose, but I'd go with a hybrid car BLDC or PMAC motor...

Yes, but the question was whether or not the 3-phase AC industrial motors that vrsi367 has are useful.

 

[MattsAwesomeStuff]

Matt, did you miss the title, or did you assume that these are low-voltage 3-phase AC motors from something like a newer forklift?

Neither/both.

I did see that they were industrial mains-powered motors, but I didn't consider that their voltages are likely well above "normal" voltages, and probably 480vac, not 220vac.

3600 rpm is in the right ballpark.

is 208 VRMS line-to-line, so the inverter would need more than 208 V DC supply. 208 VRMS would be 208*sqrt(2) V peak, or 2*208*sqrt(2) V = 588 V peak-to-peak... so you need a 588 volt battery to feed an inverter to make 120/208 V 3-phase power.

Mmmm... I'm not sure that's true, but now that you've said it, it has me second-guessing myself.

The 1.4x voltage to get peak from RMS is true, but I didn't think you need to double it again to account for peak-to-peak. The point of an inverter is that it inverts the voltage to a negative pulse. The inverter isn't like, a center-tapped transformer that gives half the voltage positive and the other half negative.

 

[brian_]

The 1.4x voltage to get peak from RMS is true, but I didn't think you need to double it again to account for peak-to-peak. The point of an inverter is that it inverts the voltage to a negative pulse. The inverter isn't like, a center-tapped transformer that gives half the voltage positive and the other half negative.

I started working through an explanation of why this is not true, because there is no neutral (it is a delta connection), and realized that Matt is likely correct. My turn to second-guess.

In a typical inverter, each of the three phase outputs is driven by two devices (such as IGBTs) connected to the two sides of the DC supply. As a result, output voltage is limited to the DC voltage, but it goes positive and negative by that magnitude: if you look at the voltage between X and Y (for instance), at one extreme X is more positive than Y by VBATT, and at the other extreme X is more negative than Y by VBATT... so the peak-to-peak voltage looks like 2*VBATT.

It's still a substantial battery voltage just to provide the low rated power, a lot to improve on that, and an unreasonable voltage if the motor is wound for a common industrial phase voltage such as 480 V or 600 V.

 

[MattsAwesomeStuff]

It's still a substantial battery voltage just to provide the low rated power, a lot to improve on that, and an unreasonable voltage if the motor is wound for a common industrial phase voltage such as 480 V or 600 V.

Yeah no argument there.

It's certainly the upper end of what commercial power would have available. I've seen motors that size on lathes for example. But anything pushing from commercial to industrial is going to be run a lot higher voltage.

~310v is okay for a conversion. 680v is not unless you're building it with 18650s, and then, I'm not sure what you'd be using for an inverter.

 

[brian_]

... and then, I'm not sure what you'd be using for an inverter.

Ironically, the most practical way to handle the high voltage necessary to use a really cheap motor is to buy an inverter which costs as much as a used EV, such as a Cascadia unit.

 

[Ivansgarage]

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