Determining Field current of seperately excited Dc Motor
Determining Field current of seperately excited Dc Motor
(OP)
Good afternoon everyone I need to determine the rated field current of a seperately excited dc motor? while the field voltage mentioned on the name plate is 250 volts dc.
Below are the Motor's Nameplate Data.
Rotor rated voltage:600 dc
Base speed:500 Rpm
Rated current:1632 amperes
Rated Power 950 Kw
Rating continous
Required forced cooling:7000 CFM (supplied forced cooling 14800 CFM)
Regards
Below are the Motor's Nameplate Data.
Rotor rated voltage:600 dc
Base speed:500 Rpm
Rated current:1632 amperes
Rated Power 950 Kw
Rating continous
Required forced cooling:7000 CFM (supplied forced cooling 14800 CFM)
Regards





RE: Determining Field current of seperately excited Dc Motor
RE: Determining Field current of seperately excited Dc Motor
RE: Determining Field current of seperately excited Dc Motor
IF you want confirmation, just look up various dc field wound motors on line and you will rated amps is exactly rated volts dc/ resistance of winding.
Often there are 2 ratings: first is the above mentioned value that will make motor go 500rpm with rated armature voltage no load, second is MIN field amps - used to tell you where to set your adj speed drive if using field weakening for higher than base speed.
RE: Determining Field current of seperately excited Dc Motor
RE: Determining Field current of seperately excited Dc Motor
If you find that the voltage required is a couple of percent below an even number, the difference in voltage from an even number will be related to the increased resistance when the field warms up.
In one of the first plants I worked at we had a synchronous motor that was started by a power circuit breaker and had a manually adjusted field voltage. One of the last jobs of the night electrical crew was to start the motor in readiness for the production shift and adjust the field voltage/current. One of the first jobs of the day shift electrical crew was to re-adjust the field voltage/current as the increased resistance when the field warmed up would have caused the field current to drop a few percent.
If you are setting protection devices allow a margin for possible higher field currents until the field warms up.
Bill
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"Why not the best?"
Jimmy Carter
RE: Determining Field current of seperately excited Dc Motor
RE: Determining Field current of seperately excited Dc Motor
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Determining Field current of seperately excited Dc Motor
I set the current at 16 amperes and gradually increasing the motor rpm and measuring both field current and armature voltages simultaneously and at the moment where the armature voltages just touched its rated volts i.e. 600 volts and field just started to begin weakening I checked motor's rpm directly at its shaft it were just a bit higher than its base rpm (say around 1%).So it seems to me the correct field amperes and make sense.
RE: Determining Field current of seperately excited Dc Motor
That's the best I can do without more information.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Determining Field current of seperately excited Dc Motor