Do I get one that's 12V or 24V or does it matter? Is it ok to use a 24V one? I have one of those. Well, it's 24V and 50 amps, not 60 amps.
Do I get one that's 12V or 24V or does it matter? Is it ok to use a 24V one? I have one of those. Well, it's 24V and 50 amps, not 60 amps.
The contacts need to be rated for 24V or more. More important is that you have wire from the batteries to the front of the boat that could handle the current. Make sure it's 6 gauge or bigger.
thanks
What size of TM pulls 60 amps? That's alot TM there. Just like to know the size of the TM?Quote:
Originally Posted by sac-a-lait
The 50 amp will work just fine.Quote:
Originally Posted by sac-a-lait
Probably none of them during normal use. But you have to take into consideration surge and stall current. You don't want the fuse or breaker popping every time you step on the go button or get into some weeds.Quote:
Originally Posted by Fisherman_Wantabe
it's a new powerdrive V2/us2, 70lbs 24V...This is what the tag says on the motor. Not something I came up with.
I have the same rig. I use a 60 amp maxi fuse and a maxi fuse holder.Quote:
Originally Posted by sac-a-lait
Del City - Wiring Products and Professional Electrical Supplies
Didn't say it was something you come up with! But I've been in the Industrial electrical trade for 28 years, and 60 amp circuit is going to be some where around 5.0hp?? That's a lot of TM! :eek:Quote:
Originally Posted by sac-a-lait
Fuses protect the wiring, not the motor. The fuse hasta be larger than the locked rotor current or the inrush motor start current. If you have electronic speed control, this circuit can source enough current to the motor briefly without self destructing.
This is what the fuse is about. I know these things.
60 amp X 24 v = 1440 W = 1.93 hp
True. But it is just not this simple when fusing motors.;)Quote:
Originally Posted by TN Hillbilly
Just correcting someone who said a 60 amp circuit would be needed for something supplying a 5 hp motor. Even at a full 60 amp load it only equals less than 2 hp on 24v.
Your right I miss the adding in my head this morning on the way out the door :( getting old.Quote:
Originally Posted by TN Hillbilly
But @ 24vdc and 60 amps that will be 2.25 hp that's assuming 1.15 eff which they should be to be rated at continous duty. And I dont think a 70 lb thurst TM is any where near that size. A 1/2hp 24vdc motor is about 2 times as large as any TM I have ever seen.
I think these are more like servo motors, than standard DC motors. JMHO
I put my amp probe on my today and at speed 100% it only pulled about 7.5 amps, its just a 55lb thurst. So go up 50% to a 70lb should only be 11.25 amps.
I'm just trying to figure these motors out, and way they call for so big of a circuit??
I may check the amps at locked rotor and just see what full load is :eek: :D
Quote:
Originally Posted by Fisherman_Wantabe
Digital probe? If so, stall it for a few seconds to get a good reading. I gave my clamp away.
Your measurements (7.5A) were at "no load" probably.
I was in the water when I put the probe on today. I can connect it right at my TM hookup, the wind was blowing pretty good and the meter was calibrated last month.Quote:
Originally Posted by Cane Pole
I also found what I was looking for just a minute ago. Looks like the 24vdc 70lb thurst motors are rated at 0.48 Kwatts of power. So that means the HP for that motor at 1.15 efficiency is just 0.644 hp and pulls only 17.4 amps. Why #6 wire and 60 amp breaker :confused:
Sorry man I did not mean to steal your post. I'm just trying to get it into my hard head why they call for big #6 wire and 60 amp breakers for these TM's. It just don't add up to me.Quote:
Originally Posted by sac-a-lait
TMs will trip big breakers even though they don't draw that much current continuously. Since you have to use a big breaker to allow the TM to operate, you need to upgrade the wire to a size that can safely be connected to a large breaker.
Locked rotor current can be from 2 to 10 times the rated full load current.
I base this on the smaller dc motors parameters I use in robots. If I build a H-bridge, I design it so to handle 4 times the current required at full load because of locked rotor current.
I am not a motor designer, but I sure have built a lot of motor speed controllers.
Max current occurs when motor is at rest and suddenly is turned on or stalled (locked rotor). By on/off operating a tm, you are constantly banging the supply (battery) with instantaneous maximum I demands.
Am I making sense?
Also, I am not familiar with the motor speed controller the TM uses. When stalled, it will probably go into current limit. So, the only true measurement for locked rotor would we direct wired without speed controller.
This is good swagging here.:)
Yes I think the controller goes into over current if stalled or over loaded. But what I'm saying is if you put a true 60 amps into a 0.48 kwatt motor it will let the magic smoke out :DQuote:
Originally Posted by Cane Pole
You have to remember that current generates heat. Heat causes an increase in resistance. Resistance causes an increase in amperage. Small dia wire has more resistance per ft than larger diameter wire. Also the longer the distance, the higher the resistance. When you step on the go button, current surges then tapers off. If the prop grabs some weeds while trolling along, again the amount of current goes way up. So as you can see there is a lot more to it than just the size of the motor.
Still if you put 60amps into a 0.48 kwatt motor it will smoke! Ask me how I know!Quote:
Originally Posted by IBNFSHN
It will spin fast.:) The fuse protects wiring, not motors.Quote:
Originally Posted by Fisherman_Wantabe
What is being left out here is the counter electromotive force. The current thru the motor is equal to the applied voltage minus the cemf. Now, you can calculate the locked rotor current by measuring the dc resistance of the motor.
For instance if the resistance of the motor is .5 ohms, then the max current would be 48 amps. This would be the locked rotor current. But the measured maxImum run current would be far less.
Remember the old CEMF.
Yea and before that 60amp fuse blows the motor will smoke :D if the specs are right and it's a 0.48 kwatt motor, that's the what the spec sheet I found said, so I think it smokes. The only way to find out is to get some one let us test his TM :eek:Quote:
Originally Posted by Cane Pole
2 battery system 24vdc (fully charged)
70lb thurst TM
2 table vices
1 amp meter
a little smoke
:D
No questions after that :D:D:D
I have asked 'em (TM folks) about specs. They play dumb.:mad:
Maybe they don't understand me.:o:o
So is the maxi fuse a 24v fuse ? I have the same issue with a couple of boats, 24 volt TM's and had the same question.
Yea they know, but they don't put them where you can find them easy :confused:Quote:
Originally Posted by Cane Pole
Most auto type (I believe) fuses are rated at 32v. Which is fine.Quote:
Originally Posted by champit
There are some that are rated at 125v too. Look on the fuse package or the fuse itself for voltage rating.
Alan,
Yu measurement at 17.5A must be pretty close. I calculated the current to be 20A@24v based on the .480Kw rating. This would not be the lock rotor current though.
As you know, I only deal with small motors.
The specs given for these small motors are (at specified voltage):
1. current at rated rpm no load.
2. current at locked rotor.
Makes my work easy.:)
Based on the Kw rate, this (60A) will not happen unless you have a fault in the motor, like shorted wiring. I smell commutators.:DQuote:
Originally Posted by Fisherman_Wantabe
On my minn kota 80# the wire drops down to #10 from the plug to the head.:confused:Quote:
Originally Posted by Fisherman_Wantabe
I know I know :confused:Quote:
Originally Posted by Allan
Yea but if the controller shorts then the motor will fry, and I would rather replace a fuse than the whole TM.Quote:
Originally Posted by Cane Pole
We also rate fuses or breakers in a circuit to protect the motor and controller before the wire. Because we have found that the thermo overloads don't always work. JMHAO
But I guess to keep your warranty good you have to follow their rules.