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From: KevinJ93 <kevin_es@whitedigs.com>
Newsgroups: sci.electronics.design
Subject: Re: Motor Speed Control
Date: Fri, 8 Mar 2024 10:30:08 -0800
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On 3/7/24 7:18 PM, John Larkin wrote:
> On Thu, 7 Mar 2024 12:13:59 -0800, KevinJ93 <kevin_es@whitedigs.com>
> wrote:
> 
....
>>
>> Stepper motors are invariably of the reluctance type. With simple
>> drivers they have a great deal of cogging, which is undesirable in a
>> capstan drive motor.
> 
> There are two types, PM and VR. PM steppers use bipolar coil drive and
> have a strong unpowered detent. And can act as generators.

Yes, I was wrong.

> Both can microstep nicely, for smooth motion.
>

Given appropriate driving circuitry that would have been expensive and 
power consuming in 1970.

> 
>>
>>> ESCAP did do a range of small stepper motors where a sine wave drive did
>>> give a uniform rate of rotation - with others you had to massage the
>>> waveform a bit to get uniform rotation.
>>
....

kw