can series fields be changed to shunt fields

[iceman10]

Hi guys, need help, I just obtained a 9.5 hp dc motor from a forklift. I want to run a sundstrand hydraulic transmission with a hydraulic pump piggybacking on the end of trans. When I took the cover off the motor I find two large bars marked A1and A2 which are the armature, also there are: 1 wire marked S1, 2 wires together marked S2, 3 wires together marked S3, 2 wires together marked S4, 2 wires together marked S5 and 2 wires together marked S6.
The S1,S2,S3 all have continuity between them but nothing to the A wires or S5 and S6, S5 and S6 have continuity between them only. Also the S wires are about #6 or #8 wires. The tag says it is a 4 speed motor (GE motor) I am thinking that the S Wires are series fields but the guage of the wire seems too light, the armature is rated at 290 amps, On connecting the motor up as a series with the A wire going to field wire S1 and then using the S3 wires to the battery the motor runs with a small current draw of only 15 amps, I am thinking that perhaps there is a way to hook this up as shunt wound, is it possible to run a series field as a shunt field? I would prefer a shunt wound so that my RPM would be steady. Can I play with the fields to get a higher rpm, any suggestions on how to test this motor would be appreciated.
Ellery Deuville

 

[aolalde]

Series windings have a few turns with low resistance. They will be excited by the armature current with a few voltage drop.
Connected in shunt or parallel to the power line will result almost in a short circuit.
Then, I do not recommend series windings being connected in parallel to the line terminals due to the destructive heat generated by the quasi short circuit current (i^2*R).

 

[motorsdirect]

Hi
In short... a series field will have to stay a series field..but to play around with speed...you could vary the supply voltage...all trial and error though!!

hope this helps
JEFF

http://www.motors-direct.co.uk

 

[laundry]

Hello
A shunt motor has slightly different operating characteristics than a series motor,since the shuntfield coils are made of finer wire,as to series motors were the series ciols are in series with the armature and pass the same current.so your answer is no.

 

[itsmoked]

iceman10 you say you want a constant speed... why not just set your hydralics up to relieve at some certain pressure then the motor would run up to some max speed and sit there. As you use the hydralics to do other work the motor would slow somewhat but why does a Zamboni care?

 

[iceman10]

Thanks guys for your replies, I am having trouble believing that the motor is a series motor because of the small wires that feed the fields,(#6 or #8) with such a high current able to go to the armature (290 amps) I would think that the series wires should be much larger. Today I tried a number of series connect combinations and the motor seemed to operate great with different RPM and current draws, for example I can arrive at these values 72 volts---- amps 70,rpm 1950 using S2 and S3: amps 45,rpm 1400 using S1 and S3: amps 130 rpm 2300 using S4 and S3 plus a number of other combination values. All were series connected and the motor was barely warm after all the testing so it would seem that series wound is the proper way to go. While I would like to have slightly more RPM I believe that I could use another battery or two to get what I want but I am pleased with the low current needed so far
Thanks again
Ellery

 

[mc5w]

Before solid state motor controllers all forklift truck and golf cart propulsion motors were series wound. The smaller DC motors that ran the power steering were usually shunt wound so that the power steering would operate at a predictable speed. The advantage of a series wound motor was that flow of large current at low speed would boost up the armature countervoltage to match the battery voltage. As the motor speeded up you would get less torque output but still within reasonable limits.

More modern forklift trucks that use solid state controllers for the propulsion use shunt wound motors and even permanent magnet motors. This is because the solid state controller measures motor current and voltage and matches what the switching power converter does to match applied voltage so that the motor operates smoothly when at less than full speed. At less than full speed a shunt wound motor will have a countervoltage that is significantly less than the battery voltage.

The advantage of a shunt wound motor with a solid state controller is that you can get full torque from zero to 100% speed as opposed to torque dropping off as speed increased in the case of series wound motors. The more sophistocated controllers for modern railroad traction motors also have the ability to turn around the switching power converter so that the motor can pump energy into the line or a resistor, what is known as regenerative braking and dynamic braking respectively.

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As a bit of historical note, steam locomotives for hilly terrain could turn their pistons into air compressors to effect dynamic braking. This was done with 5 throttle valves arranged as:

1. Live steam to piston ( controlled power output )
2. Air into piston
3. Air out or piston ( controlled dynamic braking )
4. Dead steam to stack ( produced draft )
5. Live steam to stack ( produced draft at standstill )

Early electric locomotives also had air compression pistons hooked up to the wheels for dynamic braking because stainless steel a.k.a. nichrome resistance wire had not been invented yet. Switzerland also had some electric/steam hybrid locomotives that used heat stored in a boiler to operate steam pistons when operating on sidings that were not electrified.

 

[jobbones]

Iceman10 what are the number on the side of the motor? is there a TD8-1292? P/N4896001? If so I need to pick YOUR Brain. Thanks