A customer brought in a motor for repair. It is a 3 phase motor 2 pole 400 volts off a refrigeration unit of a lorry. The customer says it is a generator.The motor has a rotor and is connected star on the terminal block.When i power the motor it runs at the rated speed.So why does the customer say that it is a generator which is run by an engine???
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MOTOR OR GENERATOR?? 2
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Right DanDel. That is assuming that you started with a given power source (i.e. utility) to begin with, and you are connecting back to the same source as a generator as you said. In his case, the prime mover seems to be the lorry which could conceivably start and run the motor/generator from a stop to begin with. If so, there is no excitation to begin with.
Actually, as I review the original post he never says. Sorry, not enough info to go any further with this really. Quando Omni Flunkus Moritati
Actually, as I review the original post he never says. Sorry, not enough info to go any further with this really. Quando Omni Flunkus Moritati
Refrigerated trucks usually derive the power from a separate small gasoline engine.
Power is supplied by mechanical or hydraulic power take-off.
When the refrigeration system uses electric motors, such as in this case, the electric power is derived from a generator coupled to the auxiliary engine.
Power is supplied by mechanical or hydraulic power take-off.
When the refrigeration system uses electric motors, such as in this case, the electric power is derived from a generator coupled to the auxiliary engine.
It would be a 'messy' way to do it, BU:-
If the AC motor is electricaly connected to an AC invertor fed from the truck 24 battery system, and mechanically coupled to the truck engine or transmission in some way. Then the fridge compressors could be driven by DC Motors.
As the AC motor is 'overhauled by the truck engine, it's DC bus would rise and charge the battery, or load sharte with it.
Setting the frequency to voltage output of the invertor would be interesting, but stranger things have been done to drive air conditioners on railway rolling stock.
Also I have used AC Invertors coupled to Paper Unwinders to supply energy to a DC bus supplying an AC motor Rewinding the same paper sheet. The Unwind acts as a brake to tension the paper and provides the majority of the energy the Rewind needs to tow the papewr of the Unwind. The rest being supplied by the mains via the common DC Bus. This saves heat lost by disc brakes used to act as a drag on the Unwind thus saving energy. Same principle different application.
If the AC motor is electricaly connected to an AC invertor fed from the truck 24 battery system, and mechanically coupled to the truck engine or transmission in some way. Then the fridge compressors could be driven by DC Motors.
As the AC motor is 'overhauled by the truck engine, it's DC bus would rise and charge the battery, or load sharte with it.
Setting the frequency to voltage output of the invertor would be interesting, but stranger things have been done to drive air conditioners on railway rolling stock.
Also I have used AC Invertors coupled to Paper Unwinders to supply energy to a DC bus supplying an AC motor Rewinding the same paper sheet. The Unwind acts as a brake to tension the paper and provides the majority of the energy the Rewind needs to tow the papewr of the Unwind. The rest being supplied by the mains via the common DC Bus. This saves heat lost by disc brakes used to act as a drag on the Unwind thus saving energy. Same principle different application.
HUNJAN:
Any induciton motor can be converted to a generator without any mechanical changes.
There are two or more methods:
One you drive a motor above its rated RPM plus the Slip % of it, then you apply power to one/three phase(s).
The motor will produce the energy into the biasing power.
So this case needs to an electric energy source to produce power.
The second method is simpler and is the use of biasing capacitors across the windings.
Again mechanical power is applied at RPM p;us the slip % of the motor.
The motor metal has a remnant magnetism that the capacitor in parallel with the inductance of the winding starts to resonate at the operating Frequency and grows fast until a full power voltage level is obtained.
There is a need of a ELC ( Electronic Level Controller) which is a voltage detector that inserts/remove resistive loads to maintain the desired output voltage.
There is an industry of small Hydro electric power plants that use induction motor as generators for a few KWs of energy at low cost.
I have used, Ceiling Fans as generators and induction motors for 40 watts to 15 KW hydro-electric plants.
Other methods are a bit more complicated, no comment at this time.
Regards
Nando
Any induciton motor can be converted to a generator without any mechanical changes.
There are two or more methods:
One you drive a motor above its rated RPM plus the Slip % of it, then you apply power to one/three phase(s).
The motor will produce the energy into the biasing power.
So this case needs to an electric energy source to produce power.
The second method is simpler and is the use of biasing capacitors across the windings.
Again mechanical power is applied at RPM p;us the slip % of the motor.
The motor metal has a remnant magnetism that the capacitor in parallel with the inductance of the winding starts to resonate at the operating Frequency and grows fast until a full power voltage level is obtained.
There is a need of a ELC ( Electronic Level Controller) which is a voltage detector that inserts/remove resistive loads to maintain the desired output voltage.
There is an industry of small Hydro electric power plants that use induction motor as generators for a few KWs of energy at low cost.
I have used, Ceiling Fans as generators and induction motors for 40 watts to 15 KW hydro-electric plants.
Other methods are a bit more complicated, no comment at this time.
Regards
Nando
Guess you have already thought of this, but in UK truck refrigeration systems it it normal to have the 'fridge plant run by a small diesel engine, with an induction motor available to keep the 'fridge plant running when the truck is in a warehouse at night, as this is more economical than unloading and reloading the truck. The engine is decoupled through an automatic clutch, so it spins the motor but the motor doesn't spin the engine. Easy way to check - see if the vehicle has a connector to bring external power onto the vehicle.
jbartos
Electrical
- Jan 15, 2000
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Suggestion to HUNJAN (Electrical) Mar 13, 2003 marked ///\\A customer brought in a motor for repair. It is a 3 phase motor 2 pole 400 volts off a refrigeration unit of a lorry. The customer says it is a generator.
///What does a nameplate say or read?\\The motor has a rotor and is connected star on the terminal block.When i power the motor it runs at the rated speed.So why does the customer say that it is a generator which is run by an engine???
///Please, would you post the nameplate data?\\\
///What does a nameplate say or read?\\The motor has a rotor and is connected star on the terminal block.When i power the motor it runs at the rated speed.So why does the customer say that it is a generator which is run by an engine???
///Please, would you post the nameplate data?\\\
Hunan:
Most all induction motors may be operated as generators.
The alternative Energy industry ( small hidro electric plants ) mayuse the indution motors as generator.
For a single phase you drive the motor above its rpm+slip and connect running capacitors to the phase winidng, the power available is about 80 % of the rated power as a motor.
For the 3 phase you may use it as a 3 phase power out or one phase out.
In both cases you connect capacitors to two of the phases with the ratio of C and 2C.
The value of the capacitance depends on the HP and the input voltage.
Also you may apply AC voltae to one winding and if you app;y RPM+Slip the motor is converted into a generator and feeds power into the grid, way to couple several sources of power to a single grid system.
I hope this helped
Nando
Most all induction motors may be operated as generators.
The alternative Energy industry ( small hidro electric plants ) mayuse the indution motors as generator.
For a single phase you drive the motor above its rpm+slip and connect running capacitors to the phase winidng, the power available is about 80 % of the rated power as a motor.
For the 3 phase you may use it as a 3 phase power out or one phase out.
In both cases you connect capacitors to two of the phases with the ratio of C and 2C.
The value of the capacitance depends on the HP and the input voltage.
Also you may apply AC voltae to one winding and if you app;y RPM+Slip the motor is converted into a generator and feeds power into the grid, way to couple several sources of power to a single grid system.
I hope this helped
Nando
Here in the states I have worked on ThermoKing refrigeration units that used an engine running a generatorand a compressor to power the refrigeration unit on a truck during the day. At night the truck was plugged into AC power, and the refrigerator compressor and the fans in the evaporator were run off AC line power. There was a centrifugal clutch on the engine shaft that allowed this. The fans in the evaporator were 3 phase...
Just my $0.02..
Anyone know the procedure for flashing the field of a single phase generator....??
damengr
Just my $0.02..
Anyone know the procedure for flashing the field of a single phase generator....??
damengr
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