RE: [PSUBS-MAILIST] 12 or 24v ? - PWM controllers

["Ken Martindale" <wmartindale@cfl.rr.com>]

On the Psubs site there is a schematic of a motor controller. It operates at
20 kHz.

Ken Martindale

-----Original Message-----
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Alex
Sent: Monday, June 25, 2012 11:10 PM
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] 12 or 24v ? - PWM controllers

If the motors are controlled by PWM make sure it's done correctly,
especially if it's regulating down from a voltage that is higher than the
motor is designed for. Sometimes people use low speed switching to regulate
motor speeds. This is like turning the motor fully on and full off over and
over, where the motor current is going to the maximum then zero over and
over. This is like controlling the motor with a resistor, where the motor
coils are the resistors. A proper PWM controller uses a high frequency and
either has an inductor built in or uses the inductance of the motor coils.
This creates a constant current through the motor which is what you want.

Alex


On 13-Jun-2012 Greg wrote:
> Hi James,
> 
>  
> 
> As they say - "voltage is your friend". Always bump it up if you can. 
> Try running the minn kotas with a PWM speed control that's being fed 36V.
> 
>  Install an amp gauge on the leads going to each thruster. Then, under 
> load, increase speed until you reach the maximum amount of amps that 
> the motors are rated for. This will be the top speed. As long as the 
> amp rating is not exceeded the motors will run fine. This not only 
> makes the whole system more efficient, but gives you more rpm on the minn
kotas without burning them up.
> This works especially well with brush motors that are oil filled.
> 
>  
> 
> Upper limit on DC systems in subs from a safety standpoint is about 50 V.
> 
>  
> 
> Greg
> 
>  
> 
>  
> 
>   _____
> 
> From: owner-personal_submersibles@psubs.org
> [mailto:owner-personal_submersibles@psubs.org] On Behalf Of James 
> Frankland
> Sent: Wednesday, June 13, 2012 9:21 AM
> To: personal_submersibles@psubs.org
> Subject: [PSUBS-MAILIST] 12 or 24v ?
> 
>  
> 
>  
> 
> Hi All,
> 
>  
> 
> Does anyone have any thoughts on this?
> 
>  
> 
> My motors are 24V minn kotas.  Do you think i should pass 12v through 
> the pods and link them up 24v inside?  Or link them up 24v inside and 
> bring that through?
> 
>  
> 
> 12v seems easier and i can run 12v things inside, but less efficient 
> and might produce more heat on the penetrators.
> 
>  
> 
> 24v more efficient and easier on the penetrator but i'll need a 
> transformer inside to run 12v equipment.
> 
>  
> 
> Ive no idea what the penetrators run at.
> 
>  
> 
> Any thoughts?
> 
>  
> 
> Many thanks
> 
> James
> 
>  
> 

--
Mailed on 25-Jun-2012.



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