OK, lets build a scooter....
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Jaap
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Is the Gavin really using that much less power than the Mako?
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quote: Aquamaniac once bubbled...
The Mako motor specs are
Speed:2.7 Mph
Thrust: 50lbs
Voltage: 24 VDC
Current: 34 Amps
Power: ~800 watts
quote: michael-fisch once bubbled...
The tuned motors George is now using turn at up to 1200RPM, burn @ 17A at 24V and produce 55LBS of thrust
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If the numbers above are correct that should imply that the Gavin only uses about half the power (17Ax24V=408W) compared to the Mako?
But the Gavin is faster, can it really be that much more efficient? Sounds like something is wrong here?
-------------------------------------------------------------
quote: Aquamaniac once bubbled...
The Mako motor specs are
Speed:2.7 Mph
Thrust: 50lbs
Voltage: 24 VDC
Current: 34 Amps
Power: ~800 watts
quote: michael-fisch once bubbled...
The tuned motors George is now using turn at up to 1200RPM, burn @ 17A at 24V and produce 55LBS of thrust
---------------------------------------------------------------
If the numbers above are correct that should imply that the Gavin only uses about half the power (17Ax24V=408W) compared to the Mako?
But the Gavin is faster, can it really be that much more efficient? Sounds like something is wrong here?
Aquamaniac
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Im just quoting from the Oceanic data they sent me.
is confusing peak power and average power.
Aquamaniac
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All motors are rated at FLA (full load amps)
What they actually draw when towing a diver, or sitting on the bench is irrelevant
What they actually draw when towing a diver, or sitting on the bench is irrelevant
The power and current draw during use is FAR more important than the "ratings".
Electric motors use power depending on the load (and their design).
I can use a motor rated at 100 HP to drive a load that is only 5 HP. Probably not very efficient.
I can also show you places where you can use a motor rated for 20 HP to actually make 100+ HP.
Useage is more important than rating.
The ratings are mostly useful when shopping for motors as it gives you something to tell the sales rep so that you get into the right series of motors. You still have to match the motor to the *actual* loads and speeds it will see in use.
Electric motors use power depending on the load (and their design).
I can use a motor rated at 100 HP to drive a load that is only 5 HP. Probably not very efficient.
I can also show you places where you can use a motor rated for 20 HP to actually make 100+ HP.
Useage is more important than rating.
The ratings are mostly useful when shopping for motors as it gives you something to tell the sales rep so that you get into the right series of motors. You still have to match the motor to the *actual* loads and speeds it will see in use.
Aquamaniac
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Respectfully, I disagree (to a point).
You need to know the FLA, so you can calculate what cable to run to the motor, what protection it requires, how much power you need to run it etc etc.
You need to know the HP rating, so you can ensure the load is matched to the motor.
The Power rating of the motor is a product of the Supply voltage, multiplied by the FLA and divided by the efficiency rating.
Amps times volts does not mean anything unless you have an accurate efficiency rating.
Im curious as to how you can get 100HP out of a 20HP motor?
(remembering that nameplate ratings at rated at shaft HP)
Dave
You need to know the FLA, so you can calculate what cable to run to the motor, what protection it requires, how much power you need to run it etc etc.
You need to know the HP rating, so you can ensure the load is matched to the motor.
The Power rating of the motor is a product of the Supply voltage, multiplied by the FLA and divided by the efficiency rating.
Amps times volts does not mean anything unless you have an accurate efficiency rating.
Im curious as to how you can get 100HP out of a 20HP motor?
(remembering that nameplate ratings at rated at shaft HP)
Dave
Aquamaniac
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My point here was, if someone tells me its a 20 amp motor, that SHOULD mean that it draws 20 amps at FULL LOAD, not 20 amps when its towing a diver, or sitting on the bench.
The nameplate ALWAYS lists FLA.
First, take an ADC 9" DC series motor, run it on 144VDC (12x12v batteries or 24x6v batteries). The normal battery load in a car will limit the run time and keep from burning up the motor. Also driving style makes a difference.
DC motors are usually current limited. You can run then on a higher voltage and make lots more HP (because the RPM is higher) without exceeding the curent limit. Lots of electric cars have 36VDC motors in them and are using 96 or even 120V battery packs.
Same thing in a DPV, we can run far beyond the designed rating because we both limit the run time and have the ability to keep the motor cooler than most applications.
I prefer to wire for more than rated current or actual current wichever is higher.
Fuses, if used are there to keep the wiring from burning up.
The nameplate is a snapshot of one point on a set of operating curves and especially for DC motors is often not even close to where you actually operate them.
Often the quoted rating is the 'continuous' rating. For shorter run times you can often make a LOT more power.
DC motors are usually current limited. You can run then on a higher voltage and make lots more HP (because the RPM is higher) without exceeding the curent limit. Lots of electric cars have 36VDC motors in them and are using 96 or even 120V battery packs.
Same thing in a DPV, we can run far beyond the designed rating because we both limit the run time and have the ability to keep the motor cooler than most applications.
I prefer to wire for more than rated current or actual current wichever is higher.
Fuses, if used are there to keep the wiring from burning up.
The nameplate is a snapshot of one point on a set of operating curves and especially for DC motors is often not even close to where you actually operate them.
Often the quoted rating is the 'continuous' rating. For shorter run times you can often make a LOT more power.
Aquamaniac
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OK, I see what your getting at, and yes I agree.
I was commenting only on nameplate data, and not considering duty cycles, over rating etc...
Fuses protect the wiring, Yes I agree there as well.
Motor protection devices protect the motor.
We are going in circles here, and it has nothing to do with the original point.
My issue was:
Volts and Amps alone do not determine how "fast" or efficient a motor is.
I was commenting only on nameplate data, and not considering duty cycles, over rating etc...
Fuses protect the wiring, Yes I agree there as well.
Motor protection devices protect the motor.
We are going in circles here, and it has nothing to do with the original point.
My issue was:
Volts and Amps alone do not determine how "fast" or efficient a motor is.
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