Speed control for syncronous motor

[3GGG]

Has anyone designed a pcb for a speed controller for an AC syncronous motor? Are these available anywhere?
I am looking at building a control to vary the frequency for a 24V motor from Berger Lahr (schneider).

[star882]

Just use a variable frequency oscillator to drive a H bridge.

[vdi_nenna]

I'm looking also. Found this but need to verify if it will work or not.

AC Motor Controller

[StevenOH]

<<I'm looking also>>
Looking for what - synchronous motor, or AC motor with carbon brushes?
Synchronous motor will require constant phase shift between the coils,
independent of frequency.

[indianajo]

The "carl's electronics" drive that vdi_nenna found is clearly for brushed motors like drills and grinders. This would be the analog of the device behind the trigger in a variable speed drill. Synchronous motors are totally different. There are now packaged Variable Frequency Drives for 120VAC single phase motors as low as 1/4 hp rating, typically stocked by newark.com and mouser.com, although I can never find them when this comes up. They cost $120-$150 in the non-AB-siemens brands. (Factories extensively use AB by siemens, for cause). You could replace your motor with a 120 VAC synchro motor, or buy a 120 vAC-24VAC transformer, whichever was cheaper. The capacitor on the motor would do the phase shifting of the second phase, as it always does.
Hammond tonewheel organs owned by rental agencies typically have one of these installed now, along with the circuit breaker ( not a Hammond feature) and the 3 pin power cord ( not a Hammond feature). This stabilizes the pitch of the organ if the gig is on generator power, which is not as stable in frequency as the house power the Hammond tonewheel was designed for. Hammond tonewheel organs use synchronous motors with a start/run capacitor.

[metalsculptor]

Speed controls for synchronous motors are ubiquitous. look for brushless DC controller chips, I am assuming the motor is 3 phase, most are and that it has position sensing , 3 sensors or an encoder are common in industrial synchronous motors (AC servo's)

An even easier alternative are the hobby motor controllers, these are sensorless controllers available in up to 120A and up to 36V input at reasonable cost, All the modern RC motors are synchronous 3 phase sensorless designs.

[wakibaki]

I have a few old car CD/radios. I thought a few times about using them to generate AC by recording, say, 50Hz on a CD and playing that...

w

[indianajo]

What is the head drive motor of a VCR? These are stacked up like cordwood at the charity resale shop for $5 each. I've stared at one, but can't get past the mechanicals without a lot more work to figure out which chip is driving the head motor.
By the way, synchronous motors in hammond organs are single phase, with a capacitor to produce the second phase.
Per wakibaki's CD trick, there are $2 IC's that produce 60 hz (or 50). Or were 25 years ago when I got free catalogs at work.

[metalsculptor]

The head motor in a vcr is synchronous but it is probably set up as a brushless DC motor. The RC motors are orders of magnitude more powerful and compact, I was looking at an 1200W motor to direct drive a 25K rpm grinding spindle and it would easily fit inside the 3" spindle body, price about A$50

There are single phase synchronous motors but they are less common than 3 phase ones, clocks and timers used to be the biggest use for these there is a laser chopper motor on my table which is single phase with capacitor. The advent of cheap feature rich controller chips, has eliminated the market for these except for some rare off mains use. At one time the mains was used as a stable synchronous time base for all sorts of things from television to fax machines and even computer hard drives. The controller chips are used in floppy disc drives and hard drives as well and they can be purchased for a few dollars from most component suppliers.

[cyclotronguy]

1200 Watt motor at 25K rpm.... low vibration in a standard 3" cartrdge.... WOW! Where can I find such a thing?

Cyclotronguy