# How to read motor performance charts



## Functional Artist (Aug 8, 2016)

This is a motor available on eBay (it seems to be very similar to a ME1003)
https://www.ebay.com/itm/Manta-10-H...m=253750423032&_trksid=p2045573.c100667.m2042

Below are the performance graphs/charts from the ad.

Can someone please explain what these graphs are saying?

Specifically, the differences between the data on the 36V chart 
...the 48V chart
…& the 60V chart

Also,

The ad says "*10 horsepower continuous duty at 48 volts"*

There are charts for 24V, 36V, 48V & 60V
...but, the ad doesn't mention 60V specifically

So, is it OK to operate this motor @ 60V?


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## kennybobby (Aug 10, 2012)

Yes it appears that they tested it at 60V, so it should be okay.

They varied the test voltage for the various charts, 36, 48, 60V. Then they would run the motor at no-load on the dynamometer and measure the speed and current. Then they step up the dyno load torque thru various values and record the speed and current at each step. From this data they can plot out the data for speed and current versus torque. Also they calculate HP using Tq x RPM and plot that out, the calculate efficiency at output HP divided by input electrical power.

The voltage determines the highest speed possible. these appear to be DC permanent magnet type motors, which have a linear torque vs current relationship. So 100 Amps will produce essentially the same torque regardless of the voltage, although the speed will be different.

So determine how much torque you need, then read up from there to intersect the various measurement parameters, which you read off using the relevant scale.


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## major (Apr 4, 2008)

Functional Artist said:


> Can someone please explain what these graphs are saying? ...


Do you know how to use an X Y graph? You know, where Y is a function of X? That is simply what these motor performance characteristic graphs represent. Torque is the load. That is the torque on the motor shaft opposing rotation. Torque is the independent variable or X, and used as the horizontal axis. At any instant in time, there is singular value of torque on that motor shaft. Locate the torque, or load, on the X axis. Draw a vertical line at that numerical value. 

The motor performance characteristic graph has several Y functions, or traces, drawn on it. These traces represent RPM, Amperes, power, and efficiency all of which are functions of the load, X. So on that vertical line which you drew at the load, X, you can read where it intersects the RPM trace, or Amperes trace, etc. That indicates the speed and current draw of the motor at that load. And at the specified voltage. As the motor performance is dependent on load, it is also dependent on applied voltage. So each of those motor performance characteristic graphs are valid for only one value of voltage applied to the motor terminals. They show you a sampling of curves at various voltage to provide a family of curves. Choose the appropriate voltage for your application or interpolate using several curves.

major


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## Functional Artist (Aug 8, 2016)

Thanks for the replies,

I used to know how to use an X Y graph, back in the 80's. LOL
It's been a while, as I was stuck driving a truck for like 30 years 


"So determine how much torque you need, then read up from there to intersect the various measurement parameters, which you read off using the relevant scale." (kennybobby)

OK, here are some specs for a Kawasaki 440LTD motorcycle (like my El Moto) 

Bikez.com states: 
Max Power 27 HP / 19 kw @ 7,000 RPM's 
https://bikez.com/motorcycles/kawasa...0_ltd_1980.php

but,
Motorcycle specs states:
Max Power 41 HP / 30.5 kw @ 7,000 RPM's
Max Torque 3.6 kgf-m / 26 lb-ft @ 7,000 RPM's
Top Speed 154.0 km/h (95.7 mph)
Dry Weight 166 kg / 366 lbs.
https://www.motorcyclespecs.co.za/mo...40ltd%2080.htm


Now, if someone was looking to go ~50MPH, on a motorcycle like this, (~1/2 of the listed top speed) it seems like they would/should aim for ~1/2 of the ICE power & torque specs?

Which looks to be ~20.5 HP ~15kw & ~13 lb-ft. 
...or ~13.5 HP / ~9.5kw depending on where you get your info.

I notice the graphs are in lb-in
...but, the ICE specs are in lb-ft

So, it looks like the 13 lb-ft would need to be converted to lb-in first.(13 lb-ft x 12 = 156 lb-in)
...but then, looking at the 36V, 48V & 60V graphs, I notice that the torque values only go up to 130 lb-in.

Looking at the 60V graph & using 120 lb-in as the "independent variable", if we follow it up to the 
...Amps "trace" (red dash line) & follow it over (to the relevant scale) it looks like its reading ~115A
...Watts trace (lt. blue dash line) ~5,800W
...Volts trace (black dash line) ~60V
...RPM's (solid black line) ~4,100 RPM's 
...EFF (dk. blue dash line) ~87% 

So, does all of this data indicate that, when operating @ 60V this motor should produce 
...~120 lb-in of torque
...when running ~4,100 RPM's
...while drawing ~115A 
...& operating ~87% efficiency?


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## kennybobby (Aug 10, 2012)

How much will the bike weigh with the driver?

How much range do you want?

How quickly do you want to accelerate to 50 mph?

From this data you can calculate the energy and power needed in order to size the motor and battery pack. 

Just from an initial look, i would say there is not enough torque available from this motor for your application.


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## Functional Artist (Aug 8, 2016)

kennybobby said:


> How much will the bike weigh with the driver?
> 
> How much range do you want?
> 
> ...


Weight: converted to electric it should weigh ~350lbs. plus ~150 for rider, so probably ~500 lbs. total.

Range: at least a 1/2 hour (~30 miles+) 

Acceleration: Decent (not whiplash fast but, not moped mode either)



I already have a motor like this on my El Moto.
...when I ran it at 36V it would top out at ~25 MPH & last ~20 min. (3-12V 35AH SLA's)
https://www.youtube.com/watch?v=ad4XPYfwluY&t=1s

...when I ran it at 48V it would top out at ~35MPH & last ~20 min. (4-12V 35AH SLA's)
https://www.youtube.com/watch?v=nBU6qdzbzdc

…& it also topped out at ~35MPH & last ~30 min. when running at 45V (2 kWh Chevy Volt lithium)
https://www.youtube.com/watch?v=5vRUdxZ334g&t=170s 

Now, I'm doing this research because I'm interested in possibly moving it up to a 60V (2.5kWh) lithium battery pack 
...kinda like this:
https://www.ebay.com/itm/LG-Chem-So...r-16-Cells-2-6-kWh-each-64-volts/142700202089
...which should provide a little more speed (~45MPH) & a bit more range.


* If I am understanding this right, this type of motor should produce ~ the same torque @36V, 48V &/or 60V.
...it's just that when running at each voltage, the torque will be spread out over a larger RPM range.

** So, when operating @ 60V this motor should produce 
...~120 lb-in of torque
...when running ~4,100 RPM's
...while drawing ~115A 
...& operating ~87% efficiency?


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## kennybobby (Aug 10, 2012)

That is correct according to their chart, but if you calculate the efficiency by hand it comes to ~84%.


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