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-----Question for MKS4F044706B00JH00 Please Put your question below----
Can this capacitor be used as a phase shifting capacitor for start up of an AC synchronous motor and run of this motor. The circuit is driven by 16V AC 150mA voltage. Or would the choice be more toward a capacitor that is X2 rated for continuous AC operation like a MKP series?
I have limited experience with this but my initial impression is you would typically want to find a capacitor characterized as a motor start/run capacitor for this kind of thing. I’m asking around to see if anybody else has input on this.
Motor start capacitors are often of a bipolar electrolytic type, because they’re cheaper and smaller than film types for similar ratings and only connected for a few seconds at a time when a motor is coming up to speed.
Motor run capacitors are typically connected the entire time a motor is running, and usually a film type due to the greater reliability/durability of such in AC applications.
Is there a typo here somewhere? 16VAC is low enough that just about any non-polar capacitor could likely serve.
In context of AC line voltage applications, there are often application-dependent regulations that apply. A safety (X#) rated capacitor could be a good starting point, but looking for a device that carries any additional qualifications that might be called for by the application/jurisdiction is best practice.
That said, the product in question does not appear to be a regularly stocked item and would be looked on with disfavor by many for that reason alone.
Hi wilsonmd,
Is this a motor for an audio turntable (record player)? I see that they sometimes use a motor with similar specs.
I am not particularly an expert on such devices, but if it does indeed operate at that low voltage (16V ac), I’d be surprised if specialty safety-type caps would be required, though it certainly shouldn’t hurt.
As @rick_1976 noted, the MKS4F044706B00JH00 is not a stocked part for us, which means you would have to order 760 of them and wait the full lead time for them to come in.
Based on the assumption that it is that low a voltage rating, here’s a link to some standard film caps rated for 4.7uF and at least 30Vac for your consideration. I’d look for ones that physically fit your requirements and then filter for higher voltage ratings and perhaps an automotive ratings to increase the level of reliability.
David:
Thanks for your thoughts. Yes, this is from a Thorens TD-147 turntable that uses the AC syncro motor. It comes with a factory wall wart that produces the voltage mentioned. The condition I am seeing is the motor is not starting all the time. When it fails to start, it is vibrating like it is attempting to sync the other pair of poles, which is what the capacitor (old one is Philips MKT 4.7uf/10/100) does. To quote from their service manual “relay contact closes, starting the low-voltage synchronous motor. C101 (the Philips cap) is the phase-lead capacitor, while the other two small electrolytics suppress switching disturbances at contacts of the start switch and relay”.
I am getting conflicting points of view from others that I have asked regarding the type of cap to use as a MKS4F044706B00JB00 has been installed and the problem of non-starting vibration persists. There has been a point of view advanced that the issue is that the MKS being a polyester capacitor cannot provide the stable phase shift or handle the continuous load required to reliably start the motor. Therefore the appropriate choice is a polypropylene capacitor that has an inherently more stable phase shifting characteristic that allows for a precise shift and thus reliable startup and run potential.
As my knowledge of capacitor material makeup and design parameters is quite limited, I thought I would seek some professional opinions of the details and possible choices. Or, the reality of my situation is that the motor has reached its EOL.
When replacing a part doesn’t resolve the symptoms, that’s a good indicator that the replaced part wasn’t the problem, or at least the entire problem. An open/intermittent motor winding of bad connection somewhere could be expected to produce the sort of result described, and would be a thing to look for.
Be advised that “audio” is a topic which seems to attract more than its fair share of folks who fall on the tragic side of the Dunning-Kruger effect. One does well to limit the trust placed in the counsel of such a population…
The difference between polyester and polypropylene capacitors for the purpose in question is probably akin to the difference between the sports and business sections of a newspaper for lining a bird cage. Are there differences between the two? Yes. Do they matter for the task at hand? Probably not. Will the most premium capacitor money can buy solve the problem if the issue is in fact a bad motor winding? Nope…
