Denny,
AC variable freq controllers as use on industrial motors use an FM scheme to drive the motor. although not a sine wave the power curve simulates one. Because the large number of ICs produced for these controllers I can't believe that lower voltage brushless motors don't use the same tech to do the job.
The simplest DC motor controllers can use a simple PMW system with a single transistor sinking to ground to complete the circuit.
Controllers that reverse the direction of a DC motor use an H bridge to control direction.
Mixing and matching motors and controllers without understanding the methods that the motors are controlled, can make a very painful to the pocket journey. If there is a motor you intend to use, then ask the controller people to assist you in your selection of controllers for your motor.
First spec out your drive requirements.
Then spec out components to meet your requirements
Components may be based on reliability, price compatibility, voltage, or whatever seems most important to you. You may find that supply is the biggest factor, as many have found. Not every component is readily available as the manufacturer would like you to believe. Your cruising ground may change ideal components to likely available components. Waiting for replacements, and country duties, can quickly make one component a bad choice.
Proven reliability makes one component shine over newly developed components that only have the manufacturers claim for reliability.
Kevin Pemberton
On 09/09/2010 08:56 AM, Eric wrote:
Denny,
Because an AC inductive motor needs true AC, I'm 98% sure that controllers like the Sevcon Gen4 are vector control because they can be used for an inductive motor as well as a PMAC motor.
On the other hand, I'm about 90% sure that the Millipak is a BLDC block commutating controller because they list it as a DC controller, though I have not checked directly with the manufacturer.
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, "dennis wolfe" <dwolfe@...> wrote:
>
> Eric,
>
> Do you know for sure which type the Sevcon PMAC is?
>
> Denny
>
> ----- Original Message -----
> From: Eric
> To: electricboats@yahoogroups.com
> Sent: Wednesday, September 08, 2010 8:34 PM
> Subject: Re: [Electric Boats] Mars PMAC and Kelly Controller
>
>
>
> Doug,
>
> You should try to find out if the Mars PMAC is optimized for BLDC or A/C vector control. Here's some info about the differences:
>
> "Although BLDC motors are practically identical to permanent magnet AC motors, the controller implementation is what makes them DC. While AC motors feed sinusoidal current simultaneously to each of the legs (with an equal phase distribution), DC controllers only approximate this by feeding full positive and negative current to two of the legs at a time....
>
> Fair winds,
> Eric
> Marina del Rey, CA
>
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