Do I Need A Magnetic Motor Starter?

Everyone needs a magnetic motor starter, this is how electric motors work (-:
Rotating magnetic fields make the wheels go round and round.
 
Bi11Hudson said:
You actually have several questions, as points of conversation. All in all, there is no good news. You have stretched your electrical service to about its' limits now. Going any further will require at least an electrical upgrade. As a renter, you know how far that would go. Like others have said, relocation is the best answer.

Now, to your basic question. A "motor starter" is simply a very large relay with the addition of a thermal protective circuit for the motor. I personally recommend a starter for some 3/4 HP motors that run a high(or continuous) duty cycle. That's both single and poly phase. At one(1) HP, that's any motor. My personal opinion, now. There are 5 HP motors that run off a disconnect but I don't approve in the slightest. A fire just waiting to happen. A burnt motor at best. Such devices are not sharable. One motor per starter. Period, non-negotiable.

There is one possibility here. You state you have a gas dryer. Look on the back wall for a "crowfoot" plug, behind or very near the dryer. If there is one, there is a source of 220-240 volts with 30 amp capacity. If it's there... ... That's your only out, unless, of course, you don't need the kitchen range. With a teenager in the house, I won't go there. I have pulled such shenanigans in the past, at remote office locations. But won't recommend it.

Your second question is about rotary phase converters. The first question would be "how many motors" will you run from it. If it's just the dust collector, no others, I have a suggestion for you. A rotary converter is simply a three (3) phase motor running with a few capacitors off of single phase power. Since the dust collector is run continuously, let it be its' own converter. That would cut down a bit on power usage too. A converter is sorta thirsy. There are many web sites on doing 3 phase from single conversion. I used to have it on my web site and removed it for liability reasons. It is(was) a corporate site and the insurance folks reduced my rate when I removed it.

The bottom line here is that, unless you have a dryer plug or tap into the range, it ain't gonna happen. At best, you will only trip breakers. At worst, the whole building will burn down. Don't go there. California has enough fires already. Dont start another.

Bill Hudson​
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Thank you Bill for your honest and wise response :)
 
markba633csi said:
You may be in a part of San Francisco with really prehistoric wiring- maybe even going back to the earthquake
If you don't have a 220 volt stove or dryer outlet you are pretty limited in amperage
mark
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Hi Mark,
I live in a 2 story townhouse style apartment. Thankfully, due to these buildings being built in the late 1960's, I don't have to worry about lead pipes for our water, and the I have plenty of 20 amp circuits in my breaker box (plus having centralized heating - some of our older victorians here have weird heaters powe red by steam). As for my stove and dryer, my unit uses gas where the kitchen has 3 separate 20 amp circuits, and the washer/dryer has a 20 amp circuit as well.
 
RockingJ said:
If I hear of another great fire in S.F. I will know where it started! You are already running more that I would recommend on the existing wiring, don’t add more!

The use of a contactor to control motors allows the contacts in the contactor to take the power surge when the motor starts up. This way the circuit switch doesn’t arc across the contacts every time the circuit is energized or de-energized. The contactor has much larger contact points that can take the spark better.

Another thing is you should have a motor starter in the input circuit to the rotary phase converter, the motor starter is simply a contactor with an on/ off switch and overload protection. It also will shut off the circuit if there is a power loss. This prevents the RPC from restarting automatically when power is restored.



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Thank you RockingJ for the motor starter suggestion. I will definitely look into getting one now.
 
While you might not need a motor starter per se, I might consider adding an NVR. I am slowly doing that on all of the spinny bit machines here in my workshop.

An NVR is a push-button switch panel with a relay built into it - simple device. The good part of it is that should the power go off and then back on, the machine will not restart as the contacts of the relay hold the relay energized as well - the buttons do nothing but provide a momentary electrical contact to draw in the relay.

This gadget is nice for a few reasons. It provides push-button start and stop for the machine (the stop being a big 'OH S#$% button!) as well as the NVR functionality (see above). What it does not provide is overcurrent protection.

What prompted me to do that is the forward/reverse drum switches on my lathes and mill - they have no center stop at off. In an emergency, there's no 'OH S#$% function there - going from forward to reverse simply leaves the motor energized and spinning as the start winding is already de-energized.

Just a thought - Alan.
 
As long as you have two circuits on opposite phases the "220 voltage converter" will work fine. It just grabs a +120v and a -120v supply at the same time.
As others have said the overall power available is the limiting factor. 1 horsepower equals 746 watts. No way around that. If you need to run a 2 hp motor you must draw a minimum of 1492 watts not allowing for power losses, inefficiency, and higher startup currents. If one of the circuits has a 15 amp breaker that will likely not handle it. If you had 2, 20 amp circuits on opposite phases available you might be able to safely run 2 HP. That could theoretically provide 2400 watts. Derating to 75% gives 1800 watts. If you put a phase converter in the circuit I am not sure how much efficiency you would lose in addition to the above issues.
Other may disagree with the use of the word safely.
Robert
 
Yes you need a magnetic starter as they are chock full of magic that is not easily available elsewhere.
They will start a motor and stop a motor.
They will start a motor that is out of direct line of sight, in another room for instance.
They will start and stop a motor when you are not there to push the start and stop switches manually.
They will allow the shutdown of a motor that has gone beyond its operational parameters without human intervention.
They will not defeat SkyNet however so be very careful (-:
 
RockingJ said:
If I hear of another great fire in S.F. I will know where it started! You are already running more that I would recommend on the existing wiring, don’t add more!

The use of a contactor to control motors allows the contacts in the contactor to take the power surge when the motor starts up. This way the circuit switch doesn’t arc across the contacts every time the circuit is energized or de-energized. The contactor has much larger contact points that can take the spark better.

Another thing is you should have a motor starter in the input circuit to the rotary phase converter, the motor starter is simply a contactor with an on/ off switch and overload protection. It also will shut off the circuit if there is a power loss. This prevents the RPC from restarting automatically when power is restored.



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Not entirely true. Depending on how the control for the starter is wired it could automatically restart.


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