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While I am waiting for a consulting firm (specializing in electric motors) to call me back in regard to using the right "Variable Frequency Drive" (VFD) to be used with the Santos Dough Mixer, I thought I recap some of the essential points that have been made so far (after I restate the specifications for the Santos Dough Mixer below):
Santos Dough Mixer Specifications:Model 18
Motor Type: Single-phase asynchronous/induction motor (
capacitor start motor)
Voltage: 100-120 V
Frequency: 50/60 Hz
Wattage: 650 W
Amperage: 4.5 A
Motor Speed: 1800 RPM at 60 Hz
The Problem: How to decrease the RPM (rotation per minute) of the Santos motor.
Essential Points:Mr. Holorim: "When I owned a [Santos] 18 mixer (many years ago), I managed to change the speed quite easily. Its single phase motor was fitted with a permanent capacitor (instead of a starting capacitor which is disconnected since the rotor began to run), and this allowed me to drive it via a frequency inverter. But be careful to not choose any [frequency inverter] model: theses devices are first of all made for 3 phase induction motors, but few models are able to drive single phase motor which do not have transitional state when starting (i.e permanent capacitor)..."Mr. Holorim: "In my opinion, its better to keep the actual motor, and to power it with a 3-phase inverter which can drive single-phase motor (i.e. Siemens Micromaster's range)."Mr. Holorim: "The inverter doesn't control directly the motor RPM, but produces a current with an adjustable frequency; but on an induction motor the frequency affects the RPM, which is the same goal indeed. All inverters are able to yield from 0Hz to 60Hz (and many more but it doesn't recommended to overspeed a motor which isn't designed for): then you may be able to adjust the motor at the speed you want, from 0 up to 1600 RPM with an accuracy of a couple of RPMs."Mr. Scott r: "Sounds like you [Scpizza] must have bypassed the capacitor for everything but the startup allowing the use of the vfd?"
Mr. Apizza: "So a possible fix is to defeat the centrifical switch that disconnects the start capacitor (after start) and run on a VFD? Makes sense to me." Two days ago, after I talked about this issue to another company that specializes in VFDs, they emailed me as follows: "We don't sell any drives that can be used on single-phase motors. You would need to search Google for a company that makes
drives that will work with a capacitor start motor."
Is there such a thing as a VFD that works with a "capacitor start motor"? Per Mr. Holorim, above, "I managed to change the speed quite easily. Its [Santos'] single phase motor was fitted with a permanent capacitor (instead of a starting capacitor which is disconnected since the rotor began to run), and this allowed me to drive it via a frequency inverter. But be careful to not choose any [frequency inverter] model: theses devices are first of all made for 3 phase induction motors, but few models are able to drive single phase motor which do not have transitional state when starting (i.e permanent capacitor)..." Later, Mr. Holorim added, "In my opinion, its better to keep the actual motor, and to power it with a 3-phase inverter which can drive single-phase motor (i.e. Siemens Micromaster's range)."
If I understand this whole thing properly, a tentative solution to the problem involves 2 steps:
1) Getting the right VFD, and
2) Either changing the original capacitor to a "permanent capacitor", or somehow managing to have the VFD bypass the original capacitor (without replacing it) after the startup.
WARNING: NO ONE SHOULD TRY ANY OF THE ABOVE RISKY PROCEDURES (WHICH MAY BE LIFE THREATENING) WITHOUT EXPERT CONSULTATION AND PROFESSIONAL SUPERVISION.
