No expert on motors here, so be pat

[PUMPDESIGNER]

No expert on motors here, so be patient.
ON single phase Franklin submersible motors the start relay is a simple device that feeds the start capacitors momentarily. That relay coil "drops out" when voltage sags at start up, sending current to the starting caps. As soon as voltage picks back up the relay re-engergizes and cuts power to the start caps.

Could that method be used on other motors that are normally built with a starting switch in the back of the motor?

For example: A standard single phase 5 horsepower pump motor, (215 JP or JM frame) normally has a centrifugal start switch in the back of the motor. Could that switch be removed and a starting system manufactured to operate the start windings?

If this is nuts idea just tell me. Obviously we have had problems with that starting switch sticking and failing at times.
Richard Neff
Irrigation Craft

 

[SteveKW]

Sure, you can use that type of start switch. They even make electronic switches! I too work on several of the motors each week that you describe. Considered changing motor manufacturers?

 

[PUMPDESIGNER]

SteveKW
Good idea about switching motor manufacturers.
We have tried to understand which manufacturer does the best job on single phase switches, and we have some conclusions. Best solution we have is complicated, but is as follows.

1 - On single phase installations we require a jockey be used so that pressure maintenance is done by a small pump, their start switches seem to be more reliable.

2 - We set a company policy of never using ODP motors, only TEFC. ODP motors pulling in dirt definitely causes single phase switch problems.

3 - We have a rapid cycle feature. The pump starts and stops too often we shut it down and declare an alarm. This forces operators to fix their problem instead of allowing the pumps to tear up.

4 - General carefulness in selecting pump sizes and the setting controls to prevent frequent pump starts. Could run up against re-circulation problems on the pump, but we watch for that too.

5 - I will not mention brands, but obviously some manufacturers have very bad start switches.

The reason I asked is that my preferred manufacturer does not make 7.5 hp and 10 hp single phase motors in TEFC, and as you can see we believe that TEFC is the way to go.

Any more ideas SteveKW? PUMPDESIGNER

 

[neps3]

pumpdesigner

Of course yes. You have the idea. What you need is the start time and build an external circuit (static).

 

[PUMPDESIGNER]

Our preferred vendor is Baldor. We believe they are stable, honorable, and work hard at building good motors. They do not however make JP or JM frame, TEFC, 1 phase motors, only ODP. I personally think it should be the other way around, no ODP only TEFC. Their warrantee rates would drop because ODP motors bring dirt and moisture into the single phase switch area.

In fact for many years we would not use Baldor because they could not provide those two motors. So we are now looking to use the motors that are available in TEFC and just remove their stinky switches and use solid state or relay start systems.

Thank you guys. PUMPDESIGNER

 

[jbartos]

Suggestion: Visit

http://www.motorsanddrives.com/cowern/motorterms2.html

http://www.usmotors.com

etc. for more info

 

[Marke]

Probably the best way to control the capacitors, is to use a current sensing relay and switch the capacitors in circuit when the current is over 250% of the rated current and out of circuit when the current is below that figure. This will ensure that the capacitors and in circuit when the speed is below about 85%.
Best regards, Mark Empson

http://www.lmphotonics.com