Problem with electric motor

[Graham TitmanParticipant @grahamtitman81812]

Hi i have recently bought point.3kw electric motor it will sit there buzzing but will not run unless you spin it with your finger and will then go in either direction.I was told it was working when it was removed for a 3phase conversion.I hope to use it to power a small tool and cutter grinder and wonder if it needs a start capacitor so i can use it with a nvr switch. Unfortunately i cannot get a photos to upload to a album at the moment.

[Graham TitmanParticipant @grahamtitman81812]

Needs help to Work

[Martin ConnellyParticipant @martinconnelly55370]

There is probably a start capacitor, a start coil and a centrifugal switch to switch the start circuit off when the motor is up to speed. Two possible problems that can occur with motors left in storage for a time is the capacitor degrading for some reason but possibly more likely is the centrifugal switch jamming. This is a mechanical operation and dust and grease can jam it up. It is often possible to hear a click as the switch makes contact after power is switched off when the motor is spinning down. Since you can get the motor to run I suggest running it then turning off the power and listening for this click as the motor slows. If you hear nothing then the next step is to open up the motor casing (with power disconnected) and seeing if the switch is jamming and can be cleaned and put back into use.

Martin

Edited By Martin Connelly on 08/01/2016 19:09:55

[EmgeeParticipant @emgee]

Hi Graham

Can you post the details off the motor plate ? are you sure it's not 1/3 HP as 1/3 kW sounds unusual.

Some small motors are just induction motors and need a capacitor in circuit to start and run, not all have the centrifugal switch referred to, Parvalux are induction without any switch.

Emgee

[bodgeParticipant @bodge]

The clue here is , the motor runs in whatever direction you spin the shaft ! If the shaft spins really freely it should run without having to spin it by hand and only a second or two of buzzing, but the direction it runs will be pot luck, Due to the position the rotor stopped at when last came to rest . I have a motor 1/4 hp 1428 rpm does the same thing, set it going which ever way you want by giving a spin by hand then turn the power on. Its never had capacitor fitted, there is a centrifugal switch inside and the way this is configured with the start windings makes it a run either way motor. It makes sense that ones meant to spin by hand. how else are you going to get it going in direction you want ! Yes you can use a nvr switch and i dont think there is any thing wrong with your motor, the motor i have is at least 90 years old .

b.    that is much younger than the one i have !

Edited By bodge on 08/01/2016 21:14:01

[Graham TitmanParticipant @grahamtitman81812]

Hi i hope i have just loaded two photos to a album,there should be one of the plate and another of the wiring in the connecting box. Martin i have just run the motor when i switched on it just buzzed and when i twisted the shaft either way it just run silently with a very slight hum.Graham

[bodgeParticipant @bodge]

very slight hum.Graham

Sounds like all is well then. Nice motor, run either way motors are maybe a bit rare, yours is the only other one i have heard of.

b.   best to spin motor shaft first then quickly switch power on, gives the start winding a bit easier time of it

Edited By bodge on 08/01/2016 21:43:20

[Ian ParkinParticipant @ianparkin39383]

Have you removed a capacitor?

your rating plate shows the specification needed

looks like it may be connected to your 2 spare connections on the terminal block

[Andy HoldawayParticipant @andyholdaway]

Looking at your photo of the terminal box, Z2 appears to be not connected. This is the end of the start winding and should have a start capacitor connected between Z2 and neutral.

[wheeltapperParticipant @wheeltapper]

+1 for fitting a start capacitor.

spinning a motor to start it is a good way to lose a finger!

Roy.

[EmgeeParticipant @emgee]

Agree with Andrew and if it goes the wrong direction change those 2 wires around.

Try a 6uf 400volt motor rated type to start with, should be enough to kick it away.

Emgee

Edited By Emgee on 08/01/2016 22:26:45

[bodgeParticipant @bodge]

 

spinning a motor to start it is a good way to lose a finger!

Not if you spin the shaft first then turn the power on! Also its a run either way motor!!

So how else are you going get the right direction, keep turning it on and off till it comes right! if the start windings will stand it?

b.

run either way ,as in you dont need a reversing switch.

Edited By bodge on 08/01/2016 22:34:54

[Bruce EdneyParticipant @bruceedney59949]

Pretty sure that rating plate indicates a 10uF 400v capacitor

[John HaineParticipant @johnhaine32865]

Yup. Capacitor start and run motor. Once fitted motor will start and run only one way.

[bodgeParticipant @bodge]

Pretty sure that rating plate indicates a 10uF 400v capacitor

Bruce

i think it reads that way too, it maybe the capacitor is internal, i have a 1/2hp compton/parkinson with internal start cap. But op says run either way, so one still has to give a spin to get required direction

b.

probably why he thinking of using it t/c grinder. the motor i have, the contacts & c/f switch are configured different to the other motors i have and no amount of capacitors are going to make any difference to which way it runs, its either pot luck or spin it the way you want it go

b.

Edited By bodge on 09/01/2016 00:02:45

Edited By bodge on 09/01/2016 00:31:33

[John HaineParticipant @johnhaine32865]

It's obvious that there isn't an internal capacitor, the motor is almost certainly cap start and run, you can see the ends of both windings in the connection box. I have a rather similar parvalux motor with an external capacitor which is wired in series, there's a neat little wiring trick that gives you reverse switching with a one pole changeover switch. Once the capacitor is wired in it "tells" the motor which way to run through the relative phase relationship. It's got nothing to do with where the motor came to rest. As the OP says it was removed from a machine and the capacitor was probably left behind. Just buy yourself a capacitor, they are easily available, problem will be solved. If this had a start switch you would hear it engage as the motor slows to a stop after running.

[Les Jones 1Participant @lesjones1]

I agree with the comments that the start capacitor is missing, As the motor information plate gives the rating of the capacitor I think you should get the right one (Unless you have one in stock between 6 an d 15 uF It must be at least 400 volts AC rating.) If the motor runs in the wrong directon swap over the Z1 and Z2 wires. This is one source on ebay   This wire ended one would be better as you would not need to mount it in a box.

Les.

Edited By Les Jones 1 on 09/01/2016 09:01:19

[John HaineParticipant @johnhaine32865]

Yup, just the job Les. I'll post the wiring diagram with a reversing switch.

[John HaineParticipant @johnhaine32865]

Here is the circuit. W1 and W2 are the windings. One end of each is commoned, the capacitor is connected between the others, and the changeover switch applies live to one end or other of the cap. To ensure the motor runs in opposite directions both windings need to have the same sense, I.e. Common the wires of the same colour. You need a separate zero volts on off switch in circuit too.

[EmgeeParticipant @emgee]

I agree the drawing John has provided suits a 3 wire motor such as a Parvalux but the OP motor has the ends of both windings in the connection box, this makes me believe it is possible only the start winding requires a capacitor. The resistance will be different on each winding if this is the case so is easily checked with a multimeter.

If windings are identical resistance then use a 240v10A SPDT centre Off toggle switch to fit as John's drawing, the live to the centre pins and the windings/capacitor on the outside pins, this type of switch will provide fwd/off/rev for your tool grinder.

Emgee

[Les Jones 1Participant @lesjones1]

I agree with Emgee's comments that this simple reversing method is only suitable for motors with IDENTICAL windings and no centrifugal switch. If the OP needs the motor to be reversible we can give him a diagram of how to do it.

Les.

[bodgeParticipant @bodge]

JH. Yes im well aware of the neat wiring trick you refer to , that gives reverse by a switch .i have a motor like that so i do understand what you are saying, also im inclined to agree because its a modern looking motor, and wouldnt be cost effective to make any other way. i dont think its obvious there isn`t an internal capacitor , i thought that about the compton / parkinson motor i have and i was surprised to see the capacitor inside the motor end cap ( i pulled it apart cos i thought by the way it was running i was thinking lack of capacitor was causing the problem ).turned out be some thing completely different ! The motor i have that runs either way is designed to do so by the way the mechanical centrifugal switch is configured and a extra contact, so when the motors at rest its going to be in the either this way or that way position. This motor used to my granddads and dates to about end W1 maybe early 1920s. Funny thing is it was only 7/8 years ago i figured out it was a run either way. Just thought one day ill have look see if its a goer, so plugged it in switched in on & off a couple of time and thats when i realized it didnt always go round the same way ! Anyway it was coming apart, to clear dust /cobwebs an the like and to check wiring and insulation , thats when i discovered the strange c/f switch and extra contact ! So on this motor, at least, it does matter what position its in, unless you spin it first !

tbh with the motor in op pics i would have thought it was worth doing search on google for any info

b.

thinking about it, the old granddad used it as grinder , and he always used to give the wheel a flick then turn power on!

Edited By bodge on 09/01/2016 13:27:20

Edited By bodge on 09/01/2016 13:37:47

[Phil WhitleyParticipant @philwhitley94135]

Hi All, The vast majority of single phase motors will run in either direction. They need a kick in the right direction to start them. there are various ways, both electrical and mechanical, to do this, but by far the most common is the starting capacitor. The capacitor should be in series with the start winding and centrifugal switch (if fitted) to reverse the direction of the motor you reverse the polarity of the start winding (swap the ends of the start winding over) reversing the capacitor connections makes no difference to direction of motor running. Always check that the working voltage( Sometimes written as Wkge) of the capacitor is higher than the supply voltage, 400v for single phase, and 600v or above for three phase. On some centifugal switch type motors there is a capacitor connected on the starting winding side of the switch, which can be marked intermittently rated or int rat. This type, though uncommon today, is designed to be switched out of the circuit by the centrifugal switch after starting, and is not suitable for use as a starting capacitor in a motor without a cent switch, as these stay "live" all the time. note also that this is not the same as intermittent rating or continous rating on the motor spec plate, this actually refers to the motors duty cycle.

Phil

[Graham TitmanParticipant @grahamtitman81812]

A big thank you to all who gave their time and trouble to help to sort out my problem.I think you might have sorted it out for for me. I borrowed a 10uf 400volt capacitor and wired it in as suggested to z2 and neutral and changed the u1 and u2 over to get it to run the direction i want for now.I have not tried a NVR switch yet but will do so when i have got a cradle made up to fit it .I have taken Les advice and ordered a wired capacitor and would be grateful for a wiring diagram to fit a reverse in the future .Thanks again to every body it is nice to keep learning something new.

PS i found a website that helps to interpret motor plates

http://www.gibbonsgroup.co.uk/blog/2014/03/understanding-a-single-phase-electric-motor-nameplate

[mark costello 1Participant @markcostello1]

If the rotation of the motor would be wrong, could He buy a reverse capacitor to change direction, or must it be plugged in the other side of the room to get the other phase?

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