Discuss trying to understand 3 phase motor/capacitor installation in the DIY Electrical Advice area at ElectriciansForums.net
As others have said,the 3 phase motor must be connected in delta to work off 240v.The capacitor produces another phase.Live and neutral go to 2 motor terminals and the capacitor goes between live and the other motor terminal.Nowhere near as efficient as running on true 3 phase.is thaT GOOD?
thats interesting, am starting to see the complexity of it. are the data plates the ones inside the plastic box, i couldn't see the mention of "240v"I think it would be an idea to have a look at the other data plates which are partly shown in the photos of the contactor terminations.
Before my time but perhaps at that time most of the motors were manufactured the same but their individual control methods varied depending on application..or it could just be an hadoc build from a very resourceful electrician.
Few ways to test the capacitor;
Digital multi meter on the capacitor setting.. I don’t like this method
Do you have an analogue multi meter (not digital, type with a needle)
Set it to ohms and apply probes to corresponding terminals on capacitor, needle will move up high and then drop. If nothing happens then it’s not charging..
Other way is to get say a 9v battery, apply to the capacitor and charge it up.
Set meter to dc V and the reading should be about 9v and then it will discharge quickly through the multi meter
i cant find that photo, which is it plsI think it would be an idea to have a look at the other data plates which are partly shown in the photos of the contactor terminations.
I gave you a disagree James, solely because I seriously doubt any self respecting Electrician that professes to understand how a poly phase motor works would attempt to stick 230 V on said Machine. a Poly phase motor does not incorporate a start and run winding or a Centrifugal switch on it's shaft, why would it, a Polyphase motor. incorporates DOL, S/D, there are some modern soft starting method which I have no experience of, or in some cases a wound Rotor to aid the initial starting.it looks like something is missing from the L2 connection on the top of main contactor. could you have a 3 phase motor being used with a single phase supply incorporating a start capacitor, a run capacitor and a centrifugal switch to change from start to run?
if so then it looks like the run cap. is missing.
I'm a qualified mechanic but always tackled small electrical jobs without incident. wonder if i can get some advice re a 60's potters wheel.
it consists of :
-a 220-250 volt 3 phase, c/s 50, motor
-an largish oval capacitor [with a resistor between the 2 contacts] some distance away from motor. A 2 core cable runs from the switch box directly to the capacitor.
-a switch box on outside with 2 buttons, one for on and the other i assume is reset or off.
when switched on it runs extremely slowly for 10 seconds then stops, if you wait for a minute and press what i assume is the reset button, it will start again.
during the 10 seconds it runs you can stop it with one finger at which point it reverses direction.
any help in understanding this installation and why its not working would be much appreciated
m
Either way get a pro to help.
The capacitor has died, on startup it stores a charge which looks like a low voltage on one set of windings.
That makes sure the motor runs in one direction only at startup.
The resistor (looks about 47 meg ohms) is there to drain the charge when the motor is not running.
Make sure to replace it
As mentioned in previous posts , the motor windings must be tested so see if there is any damages to the insulation . You ll need an insulation tester and carry the test at 500v .If you do not have the equipment nor knowledge I suggest you pass this on to an electrician .
its suggested by some people here that i replace the cap, but i did test it. does the test result mean anything ?
also no ones mentioned the fact that the motor smokes, which i reported, is that significant ?
thanx
thanks, thats very interesting and obviously important, it might never have occurred to me.If the motor is smoking then there is every likelihood that the motor windings are damaged, this is probably because when you start the motor it trips on overload, you have then attempted to restart it on more than one occasion without allowing it to cool down sufficiently. Heat will damage the motor windings. If a motor trips on overload (momentary overload) it should be given sufficient time to cool down before attempting to restart it i.e. both the thermal overload and the motor. If it cannot be started within a couple of attempts then there is something seriously wrong and a proper investigation should be carried out.
In most industrial applications when a motor trips on overload the operator maybe allowed to attempt to restart it once. If this attempt fails then he is prevented from any further attempts by the drive automatically locking out, this feature is to prevent the motor from burning out by constantly being asked to start and failing.
Capacitors need testing at full working voltage , in the case of 240 volts its about 400, a digital multi meter is not suitable.thanks, thats very interesting and obviously important, it might never have occurred to me.
as the speed control is by the cone [shown] i will just fit a single phase motor which will run continuously at one speed. if i can adapt it to the cradle [shown]
i want to thank everyone for their input, ive learned a lot from your comments
m
Reply to trying to understand 3 phase motor/capacitor installation in the DIY Electrical Advice area at ElectriciansForums.net
We get it, advertisements are annoying!
Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.