# volts ? on spec sheet , A00-4009, 6HP



## clintster7 (Jun 29, 2010)

hey its me again, with questions about electric motors.. learning a lot..

here is a spec for a 6hp dc motor..

Configuration:	Four-terminals (3/8"), single-shafted, face-mounted, internal fan-cooled, reversible
Weight:	50 lbs.
Dimensions:	6.62" diameter x 10.39" body
Drive Shaft:	0.875" diameter, keyed, protrudes 2.28"
Tail Shaft:	None
Operating Voltage:	36-72 volts DC
Operating Current:	80 amps continuous, 100 amps (1-hr. thermal rating), 350 amps intermittent
Horsepower:	6 HP continuous, 6.4 HP (1-hr. thermal rating), 28 HP peak at 48 volts
Insulation:	Class H (180 degrees Celsius)
Bearings:	Sealed, using high-temperature grease
.....................................................................

I have a few questions about the motor specs.

28 hp peak at 48 volts. why is the operating voltage 36-72 ? 
I am obviously new to some of this so layman terms .. to accompany all the tech talk please . 

ill start with that and see where that takes me


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## major (Apr 4, 2008)

clintster7 said:


> hey its me again, with questions about electric motors.. learning a lot..
> 
> here is a spec for a 6hp dc motor..
> 
> ...


Hey, a motor is a motor. You can put any voltage on it you want to. It will behave differently. They are just telling you that this motor is good at 36 to 72 volts. And, if you run it on 48 volts, you'll be able to get a peak power of 28HP.

Personally, on this motor, I would not take 28 hp at 48 volt to the bank 

major


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## clintster7 (Jun 29, 2010)

major said:


> Hey, a motor is a motor. You can put any voltage on it you want to. It will behave differently. They are just telling you that this motor is good at 36 to 72 volts. And, if you run it on 48 volts, you'll be able to get a peak power of 28HP.
> 
> Personally, on this motor, I would not take 28 hp at 48 volt to the bank
> 
> major


ok so they just do not put the hp rating at 72 volts ?


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## clintster7 (Jun 29, 2010)

now on the amp side of things . what is the standard definition of "*intermittent*" in 
*350 amps intermittent*
what I am asking is about the formula they use to use that term .. ?

example would be how the cca are calculated .. 

another question i have is about motors in general .. is the amp rating on the motors how many amps it will pull from any battery larger than the amp rating .. 

example .. a 12 v motor with a 350 intermittent rating hooked up to a 12 v battery capable of 3000 amps ..


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## major (Apr 4, 2008)

clintster7 said:


> now on the amp side of things . what is the standard definition of "*intermittent*" in
> *350 amps intermittent*
> what I am asking is about the formula they use to use that term ..


There is no standard of which I am aware.



> example would be how the cca are calculated ..


This makes no sense.



> another question i have is about motors in general .. is the amp rating on the motors how many amps it will pull from any battery larger than the amp rating ..


Sorry, again, this question makes no sense. The amp draw for a motor is dependent on the load and the current limit of the controller.



> example .. a 12 v motor with a 350 intermittent rating hooked up to a 12 v battery capable of 3000 amps


Again, this makes no sense.

The current which the motor will draw is dependent on the motor design, applied voltage, conditions at the time of interest, like the RPM and load. 

Again I recommend that you learn about motors and batteries and electrical theory before jumping into deep end of the EV pool. I can answer some questions here and there, but I cannot teach you the basics. Get a book from the library, find some educational web sites, enroll in a course, or search this site for past posts relating to the subject.

Regards,

major


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## clintster7 (Jun 29, 2010)

major said:


> There is no standard of which I am aware.
> 
> 
> 
> ...


lol .. on the first "this makes no sense .. cca ( cold crank amps ) on automotive batteries .. 
cut and pasted this v

Cold cranking amps (CCA) is a measurement of the number of amps a battery can deliver at 0 ° F for 30 seconds and not drop below 7.2 volts. 

what I was asking is intermittent is 350 amps for how long ? 5 seconds, 20 seconds.. what is the standard .. you already answered that one ..

on the .."another question i have is about motors in general .. is the amp rating on the motors how many amps it will pull from any battery larger than the amp rating .." 
what Im asking is that when a motor is under load and the amps increase in the motor . Is it the motor that dictates how many amps it would draw from the battery ? would it draw the same amps from a higher amp battery as a lower amp battery ? 

so the controller is the sole unit that gives it its amps . and its extra amps under load .. ?

sorry for the inconvenience .. believe me when I say my learning curve is very active .. I have the basics down I think I am just examining spec sheets and some of the specs are vague at best .. 



This what I think I was missing in knowledge but understand i think.
The rpm of the motor is controlled by the voltage input and the amps help in the acceleration up to the voltage rpm .. so a large dc motor could only be run to say 3000 rpm (example) but could have unbelievable torque up to that number and AMPS is what helps get it there .. 

thanks for your time .


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## major (Apr 4, 2008)

clintster7 said:


> Is it the motor that dictates how many amps it would draw from the battery ?





major said:


> The current which the motor will draw is dependent on the motor design, applied voltage, conditions at the time of interest, like the RPM and load.





clintster7 said:


> would it draw the same amps from a higher amp battery as a lower amp battery ?


The type and size of battery will affect the voltage/current characteristic. In simple terms, a better (often bigger) battery will have higher voltage as the current increases. This drop in voltage at the battery terminal is often referred to as sag or droop. I explained this to you in your thread on batteries where I used the internal resistance in the calculations.

So the influence the battery capacity and characteristics has on the current draw for a motor connected to it under load is found in the voltage applied to the motor.



major said:


> The current which the motor will draw is dependent on the motor design, *applied voltage*, conditions at the time of interest, like the RPM and load.


Hope that explained it for ya 

And I am aware that CCA stands for cold cranking amps. I just have no idea how this is relevant to the motor in this discussion. 


clintster7 said:


> example would be how the cca are calculated ..


Regards,

major


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## major (Apr 4, 2008)

Hey clint,

Please take some time and read over these threads. And as I have been suggesting, do a forum search, or get a book. Your comments suggest to me that you do not understand how the current draw for an electric motor is a function of several things and not just a number you can run with.

Hope this helps.

major

http://www.diyelectriccar.com/forum...ng-motor-specs-and-vehicle-gearing-27320.html

http://www.diyelectriccar.com/forums/showthread.php/electric-motor-output-wrt-voltage-32492.html

http://www.diyelectriccar.com/forums/showthread.php/dc-motor-graph-39649.html

And an example motor performance characteristic graph:


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## clintster7 (Jun 29, 2010)

thanks will do


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## clintster7 (Jun 29, 2010)

I am looking at the graph above and trying to take it all in so am I reading it correct ..

the Tq is the variable right 

so if you follow straight up the 30 lbs line on the graph .. 

so for the motor to have 30 ft/lbs at 2900 rpm ,200 amps are needed ?

so the motor has less tq and hp the higher the rpm but the less amps are used . 

or am i mixed up


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## major (Apr 4, 2008)

clintster7 said:


> I am looking at the graph above and trying to take it all in so am I reading it correct ..
> ...........
> or am i mixed up


Clint,

I think you're on the right track.



> the Tq is the variable right


Torque is the independent variable, or X axis, the horizontal axis.



> so if you follow straight up the 30 *lbs* line on the graph .


That would be a torque value of 30 lb.ft. (pound feet). Please try to keep the units correct even though the fellow who drew the curve used "Ft/Lbs" which is totally incorrect 



> so for the motor to have 30 ft/lbs at 2900 rpm ,200 amps are needed ?


Again, at 30* lb.ft.*, which is the load (torque on the motor shaft opposing rotation), then the motor will draw 200 Amps and rotate at 2900 RPM if 72 volts are applied to the motor. Furthermore you can also read that the power output is 16.5 HP and efficiency is 86 or 87%.



> so the motor has less tq and hp the higher the rpm but the less amps are used .


Don't forget this is the motor behavior at a constant voltage applied. And the way I look at it is the motor slows down as it is further loaded. Increase the load (torque on the shaft) and the RPM fall, current goes up and HP goes up.

Take load away from the motor and it will increase RPM, current goes down and power goes down.

This is all when a constant voltage is applied to the motor. It is not like when you push further down on the accelerator in an EV and go faster because then you are increasing the voltage to the motor to make it go faster and produce more power.

I think I explained this in one of those links.

Regards,

major


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## clintster7 (Jun 29, 2010)

ok good .. 

In the 3rd thread you gave me to read he explains he is looking at motor graphs to find a motor comparable to a golf cart motor he is wanting to buy a controller for .. 
((he quotes ...))
"Voltage is no problem as most are good up to 72 to 96 volts, but there are a lot of current options and the price goes up with current as you know."

my question to this quote is .. 
according to a motor graph , a set amount of load ,at a set amount of volts will only draw a set amount of amps .

This tells me that it is not the controller that sets the amount of amps a motor will use at a specific load .. he is only talking about looking for a controller that can handle the amount of amps that a motor will pull ..
( correct ?)

So a battery pack that is capable of more amps than the motor will pull at a specific (load,rpm) is not controlled by the controller but by the motors need ..
Example using the graph you gave me ..
30 lbs then the motor will draw 200 Amps and rotate at 2900 RPM if 72 volts are applied to the motor.

so just because a battery pack may have 1000 amps available the motor will only pull what it needs and its not the controller that keeps the amps at 200 its the motor .. the controller gives the volts and has to be robust enough to handle the amps for the specific motor .. 

I have been under the impression that controllers controlled amps and volts ..


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## major (Apr 4, 2008)

clintster7 said:


> I have been under the impression that controllers controlled amps and volts ..


Controllers limit current and control voltage. 

See post #2 in this thread. http://www.diyelectriccar.com/forums/showthread.php?t=46784 Sure at 72V and 30 lb.ft., the Warp9 motor will draw 200A. That is true whether you have a controller or not. But how did you get your vehicle up to that speed? Or what happens if the vehicle speed changes for some reason? Then the controller will be real handy.

It's a dynamic world.

major


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