start and run capacitors - quick answer??? 1

[jethrow]

We have a hydraulic press with a large 230 VAC single phase motor in it. The maintenance worker sat a 660V 90uF electrolytic running capacitor on my desk and said it was bad. This turned out to be true and I got a replacement. Trouble is he did not make a diagram of which wires came from where.

There are two starting capacitors (430uF) wired in parallel with one (approx 14 ga) lead going into the motor and the other (same size) to be attached to the running capacitor. There are two more 14 ga. wires from the motor to be attached to the cap with the fouth and final wire (10 ga) from the control panel (AC line in).

Question 1: Should the line in and one of the 14 ga. wires from the motor be attached to one side and the other 14ga. from the motor and the 14 ga from the starting caps attach to the other?

Question 2: The nearest replacement cap was a 660V 80uF. A 90uF could not be found anywhere. Will this work?

DISCLAIMER: I know I probably need to furnish more info and will gladly do so if these questions cannot be answered based on info given.

tia
Steve

 

[skiier]

Jethrow look a the motor and find a nameplate if u can. u may find a schematic there- unless someone has removed it. 90% of motor manufacturers ensure some sort of schematic appears somewhere. Look again. Is it dual voltage? How many leads come out of the motor? My guess is that it is a simple dual voltage motor. It probably has 4 windings. Meaning 8 leads out the motor. I know I will get corrected here by everyone on other types of motors but I am just reffering to the most common type of dual voltage motor out there. If the wiring hasn't been touched - other than what your guy did - then examine the wiring as is. I mean the cap will wired in "series" with a winding and you seem to understand the difference between series and paralell circuits.
Since u describe an industrial installation the motor may in fact have been designed solely for 230vac. Then in it's simplest form the motor would have 4 leads coming out of it. 2 leads connect directly L1 and L2 and these leads are the "in phase" winding in the motor. The other two leads are the "leading" phase winding and they are connected in series with a capacitor - or some combination thereof as u hav described - to L1 and L2.
If it is a dual voltage motor then you will probably see 8 leads in the motor box. For a high voltage connection you should see 2 sets of leads connected in the motor box. The other 4 leads are your "in phase" and "leading" windings. As I described above 2 leads go directly to L1/L2 while the other 2 leads are connected 2 L1/L2 via a series capacitor.
An 80uF cap will be fine just use the right cap type for the application- this is very important.

Give us more info and we can tell you how to connect it.

 

[jbartos]

Suggestion to jethrow (Electrical) Dec 8, 2003 marked ///\\We have a hydraulic press with a large 230 VAC single phase motor in it. The maintenance worker sat a 660V 90uF electrolytic running capacitor on my desk and said it was bad. This turned out to be true and I got a replacement. Trouble is he did not make a diagram of which wires came from where.
///There should be two wires or two groups of wires only, if a (two-terminal) capacitor is removed.\\There are two starting capacitors (430uF) wired in parallel with one (approx 14 ga) lead going into the motor and the other (same size) to be attached to the running capacitor. There are two more 14 ga. wires from the motor to be attached to the cap with the fouth and final wire (10 ga) from the control panel (AC line in).

Question 1: Should the line in and one of the 14 ga. wires from the motor be attached to one side and the other 14ga. from the motor and the 14 ga from the starting caps attach to the other?
///It is probably better to contact the manufacturer tech support.\\Question 2: The nearest replacement cap was a 660V 80uF. A 90uF could not be found anywhere. Will this work?
///11% in lower capacitance will mean 12.5% higher Xc which will reduce the current. This might work if the motor is not fully loaded since this impacts the motor torque.\\DISCLAIMER: I know I probably need to furnish more info and will gladly do so if these questions cannot be answered based on info given.
///Furnish the motor nameplate data.\\\

 

[SteveKW]

Here is a diagram that may help...

http://www.exico.co.uk/single-phase-revers.pdf

Jb is correct about the smaller capacitor... as a rule if the same size is not available, go the next size LARGER!

 

[rbulsara]

Refer to the following link, one of the connections should match yours.

http://www.lmphotonics.com/single_phase_m.htm

If link is truncated type in .../single_phase_m.htm after .com/

 

[jethrow]

Thanks to all for the information. I have resolved this issue with the help of your plentiful responses.

Steve