CR4® - The Engineer's Place for News and Discussion®

 Previous in Forum: Heat Treat Calculations Next in Forum: Speed Control of a Brushed Starter Motor
Associate

Join Date: Sep 2009
Posts: 35

# Motor - Alternator Set 6.6 KV 400 HP

08/07/2017 2:21 AM

Dear Sir

60 years old MA Set 400 HP 6.6 KV 12 POLE/ Alternator capacity is 440 V and 60 cycle used in shipping industries dry dock -- 2 nos-motor same design has come for repairs where rotor winding clip flash over and second one for overhauling.We have noticed Rotor is having 4 ring slip ring and two windings of are connected start and end. third winding kept dummy. 4 ring slip ring connection goes to panel resistance bank . When we check slot coils getting magnetizing there are 3 slots adjacent each pole pitch are not getting magnetizing where winding are kept dummy.Total no slots 89.How this rotor function as slipring rotor.Both the rotors are different winding configuration one rotor each winding resistance is 105 milli ohms and second one rotor winding resistance is 52 milli ohms .How thee rotors of same capacity is having different resistance value

Interested in this topic? By joining CR4 you can "subscribe" to
Guru

Join Date: Dec 2010
Posts: 1283
#1

### Re: Motor - Alternator Set 6.6 KV 400 HP

08/07/2017 4:02 PM
2. "winding ??clip?? flashover"?
3. "kept ??dummy??"
4. "windings... connected Start and end" - connected to what?
5. Is this a frequency conversion set?
6. Are motor rating plates/terminal diagrams identical except for serial number?

On winding resistance, 52 is near enough half of 105. So maybe 1 winding of parallel 2 [each 105] is open or one of 2, each 52 in series, is shorted. And is the "panel resistance bank" identical for both machines or different to fit different rotor resistance/voltage?

Look at circuit diagrams for machines for difference.

Associate

Join Date: Sep 2009
Posts: 35
#3

### Re: Motor - Alternator Set 6.6 KV 400 HP

08/09/2017 7:20 AM

Slip Rotor bar construction and joints are made at overhang end , clip are used for brazing joints. Since only two winding are connected to slip rings rings 4. Third winding not connected and kept as dummy winding not connected to slip ring which may function as damper winding. Motor is 6.6 KV and alternator is 440 volts 60 cycles

No drawing is available , Name plate does not give complete information

Excitor also mounted on the same shaft to give DC Supply to feed two windings when started

Guru

Join Date: Sep 2006
Location: California, USA, where the Godless live next door to God.
Posts: 4480
#2

### Re: Motor - Alternator Set 6.6 KV 400 HP

08/07/2017 6:25 PM

It's difficult to understand everything you are describing, likely due to English being a second language for you. But it sounds to me as if maybe what you have is what's called a "doubly-fed induction generator (DFIG)". This is essentially a wound rotor induction machine that can be a motor or generator and the way the rotor is powered is very different from a standard Wound Rotor Induction Motor. Do some research on that DFIG term and see if it describes what you have.

__________________
** All I every really wanted to be, was... A LUMBERJACK!.**