110volt motors

[bob531]

Hi Havent been here for a while but do 110v 50hz induction motors work just like 240v motors ,apartt from the obvious such as supply. What do you need to power one in regards to a starter or nvr.Can you just use a normal 240v starter??
Thanks Bob

 

[CHJ]

No you need to purchase a 115 volt NVR. They are available.

The holding/latching coil of a 240 volt rated unit is unlikely to hold in.

Alternate is to fit a standard 240 NVR in the feed to the supply transformer (considerably cheaper I suspect)

 

[bob531]

SO you mean like this http://www.powertoolworld.co.uk/trend-nvrs2115v-no-volt-release-switch-115v.html Bloody expensive.
The reason im asking is ive seen some 110v motors going cheaply and i need a motor for a project and have the 110v transformer so thought why not???
Whats the difference between an NVR and a DOL starter???

I have a small model makers thickness sander from the USA which i use from a 110v transformer, not sure what sort of motors in it but the box on the machine seems to have JUST a capacitor and a simple toggle switch. The capacitor is rated 250v 50/60hz which is confusing me .

 

[Myfordman]

The capacitor is rated at 250ac for a 110v motor for the same reason as we use 450v rated capacitors with UK mains - because it needs to be!

In most cases DOL and NVR are the same. DOL is more of a professional name and NVR can also refer to the cheap and nasty switches as fitted to imported machines that are solely NVRs and offer no protection to the motor. In 99% of cases a DOL will also be fitted with current protection.

 

[CHJ]

As Myfordman says, DOL starter will have an overload function to protect the motor from consuming excessive current if it is overloaded or stalled for any reason.

The 240 volt capacitor is there to add a safety factor against voltage spikes.

A nominal A/C voltage is quoted as RMS (rout mean square) is already providing voltage peaks much higher. (1.414 x the RMS value.)

Therefore 110v RMS will be peaking at 155.54 volts, and on top of that there will inevitably be higher spikes caused by poor switching contacts and associated inductance loads in motors or transformers.

Capacitors have very delicate insulation as a factor of trying to keep the size down which can easily be punctured so an extra 100 volt working tolerance is not over the top on A.C. circuits.

 

[bob531]

Right im understanding a bit better ,thanks. So if i buy a dol starter for 110v would that be all i need to power a 1/3 hp 110v 50hz motor (wired between the plug and the motor?) Or is there a cheaper way of doing it?
Thanks

 

[CHJ]

Very much dependant upon what you are doing with the motor.

Motor current protection is only necessary if there is a chance that a motor can be overloaded such that it draws excessive current for a prolonged period and can burn out or even catch fire.

No voltage Release of the supplies are a safety requirement where there is a risk of the machine starting up automatically after a disruption of supply such as a power cut where you could be caught with your hands in a vulnerable position if it started unexpectedly when the supply returned or when you have left the building, you would not want a lathe or pillar drill to start spinning when unattended for instance.

 

[bob531]

What im doing is making a 6" diamond disc flat lap , the motor only needs to be about 1/4 - 1/3 hp, (the samller footprint the better) and im trying to figure the cheapest way to do it. basically like a disc sander running vertically . Id like it to be smooth and quiet running . I did have a motor from a clarke belt /disc sander but for some reason today it decided to start smoking clouds of white smoke. (so thats out of the window.) I had last week a small motor with speed control board from an old rexon 3 wheel bandsaw (the motor was working but has suddenly decided not to,unless i have the wiring wrong.The shaft is a bit short though)
Thanks

 

[CHJ]

I would say you need a much slower speed than a straight motor drive if you are talking about a lapping plate, anything above 2-300 RPM is just going to sling abrasive or lubricant straight off the disk.

 

[bob531]

It needs to run quite fast . There will be a build in container under and extending above the sides of the disc to catch water.