Press drill malfunctioning motor

I have a far eastern clone press drill which has provided good enough service up until recently but it has now started to play up. When the motor is switched on there is noise from the motor but it does not rotate. It was once possible to get it to rotate by turning the chuck but this is no longer effective. It is now possible to get it started by releasing the tension on the drive belts and it continues to run when the tension is reapplied. If switched off, the same routine must be followed to get it to run again.

Can anyone advise me as to what is wrong? Total loss?

Mick

Hi Mike... It sounds like the capacitor has gone defective either open circuit or short circuit - if it's gone short circuit the motor will heat up very quickly. If the motors run like this it will do damage to the field coil insulation. A replacement capacitor is cheap compared with a new motor. If you've got a multimeter check out for a short on the cap other wise check out the wiring to it from the switch onwards.. Hope that helps.

John

Hello Mick,

It is almost certainly one of two possibiliies. As John says, an open circuit starter winding is the most likely which can be caused very readily by the centrifugal switch that isolates the starter winding once the motor begins to pick up speed. There is usually sparking when that circuit is broken and over time the contacts become oxidised and fail to pass current. It is an easily cleaned component with a bit of doubled back emery cloth trapped between the contacts and pulled through a number of times. It does mean opening the motor to get at it.

The second possibility is an open circuit capacitor; replace like with like to test.

A short circuit on the capacitor is usually obvious with fuse blowing

I hope that helps

Brian

Hi Mick,
If you can take a close up photograph of the motor connection box and you have a multimeter we may be able to help you to identify the connections to the centrifugal switch and start winding. does the motor have one or two capacitors ?

Les.

Thanks for the advice gents.

Les, there is only one capacitor. I will take a photo as soon as possible (I am off to the Spalding Model Engineering Exhibition tomorrow) and get back to you.

Mick

sounds like capacitor to me I always keep a spare one handy

Are you still there Les? Are these pictures any good for directing me where to stick my multimeter probes? The condenser seems to be the only component that is easily replaceable.

Hi Mick,
Your pictures 1 and 4 look like the start/stop switch so these are not relevant to the problem. Pictures 2 and 3 shows that the the capacitor is connected directly to the winding. Not to a connection box on the motor which would more than just the two connection on your motor. Picture 3 shows the terminal box but it is badly illuminated and obscured by the cover so I can't see how many wires go to each terminal. On the assumption that two wires from it go inside the motor and two wires go to the start stop switch it is not possible to get to the ends of the start and run winding to do the tests to check the resistance of the windings and continuity of the centrifugal switch. The only test I can suggest is to connect your meter set to a low ohms range to the two connections on the terminal block. Note the reading and short together the two wires from the capacitor. The reading should change slightly as you are now measuring the two windings in parallel. (The start winding via the centrifugal switch.) If the reading does change then the fault is almost certainly the capacitor. If the reading does not change then break the connection to one side of the capacitor. (This is testing for a short circuit on the capacitor.) If the reading changes this time (Going slightly higher in value.) then the capacitor is short circuit. If the reading does not change on either of these tests then the centrifugal switch is probably the fault. (It could also be the start winding but that is unlikely.)

Les.

Hi Mick & every one who has already replied to Micks problem.

I pretty sure the type of motor Mick has, does not have a centrifugal switch, I have a motor looks very much the same right down to the shade of grey paint, and no c/ switch inside it. so can only go with the replace the capacitor as already suggested.

Maybe some one can take this a bit further with the above info

Steve

Thanks for all the advice gents.......you are right Steve, no centrifugal switch.... but I replaced the condenser today and I am up and running again.

Thanks for the diagnostic Les.....I have printed it off for future reference.

Mick

The capacitor on these motors appears to have too low a peak voltage rating for reliability. Colin

According to the silk screening the original C should be sufficient voltage rating for UK single phase. If of far eastern origin perhaps the figure of 450v may be more optimism than fact.

HI Mick. Pleased to hear your drilling m/c up & running ! Many thanks for letting us know that new capacitor solved the problem.

Steve.