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No standard prescribes permitted unbalance in current for induction motors. IEC 892/2002 however, specifies permitted unbalance in voltage as 1% at the motor terminal. It is deduced that 1% unbalance in voltage will result in 6% to 9% unbalance in current. This is, therefore, grid caused activity. However, there are load related activities, such as parallel connected single phase loads or shunt capacitors that may also influence unbalance in current across the main contactor. In large motors, sometimes, unbalance in current can be seen if the air-gap eccentricity is seen. In such cases the PF in 3 phases will be unbalanced.
Wiki User
∙ 8y ago
Wiki User
∙ 11y agoFor a motor it is usually in the 10 to 15% range. If you suspect that it is the motor try this test, Move all of the phase connections one step ahead. A to B, B to C and C to A. This will not change the rotation of the motor but it will show you if the unbalance moves ahead with the new connection. If it does then the motor is the cause of the unbalance. If the unbalance stays on the same phase wires then it is the panel that is the cause of the problem. If this unbalance is on the distribution panel it should be corrected if you have the ability to balance the system. The neutral conductor will be carrying the unbalanced load current.
Wiki User
∙ 10y agoThe maximum neutral current for a three phase unbalanced system is 120 O. This is something that basically translates to an amount of amperage, or even watts.
Wiki User
∙ 10y agoThe three resistances should be within 1% of each other because they are all wound the same, probably by machine. Anythong more than 5% indicates a fault.
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How does the 3-phase induction motor acts like 2-phase induction motor if a phase is disconnected from supply?
yes the motor will run but will draw more current and the torque will be not constant means not smooth due to unbalanced current
What is the impact of phase imbalance in electrical load?
Unbalance in three phase system puts quite a negative impact on the system and the three phase loads like motor. Motors tend to draw additional current for same power output, may increase noice, may increase heat generation.Over all losses go up in the system
What is the maximum amp for motor 5.5 kw 4 pole 3ph?
power , P=1.732*V*I*power factor so, the formula for calculate the load current for a 3 phase motor is,I=P/(1.732*V*power factor)
Why one phase shows 0 Amps while a delta connected 3 phase induction motor runs?
Cause 2 phase is applied to the motor and another phase is disconnected ... in this condition ur motor cannot run longer ,it will trip on over current or burn ur motor winding .
How do you make correct setting for overload of a 3 phase motor?
125 percent of full current rating of the motor
Core balance ct?
CBCT used to protect the motor winding from unbalance load it is install on the cable ,in normal balance conditions the sum of the three phase current is zero so secondary current of the ct also zero .when ever unbalance occurs then this unbalance current will flows through the ct then relay sense and trip motor
What are the causes for unbalance of currents of a 3 phase a c motor?
unbalance voltage supply resistance between phase unbalance joints of coil loose winding short with body
How field current change in 'V and inverted v curves ' of synchronous motor?
In v curves armature current decreases in under excitation and increase in overexcitation as fielcurrent increases and armature current is maximum at unity power factor.The power is maximum when load angle is equal to impedance angle.A linear motor is a essentially a multi phase
How does the 3-phase induction motor acts like 2-phase induction motor if a phase is disconnected from supply?
yes the motor will run but will draw more current and the torque will be not constant means not smooth due to unbalanced current
What you basically want is will each phase take 26 Amps current for 15HP 3 phase 415VAC motor?
Yes. In a 3-phase motor, all 3 phases have the same current.
What is the impact of phase imbalance in electrical load?
Unbalance in three phase system puts quite a negative impact on the system and the three phase loads like motor. Motors tend to draw additional current for same power output, may increase noice, may increase heat generation.Over all losses go up in the system
How do you calculate the no-load current of a three phase induction motor?
All transformers, single phase or three phase have a "no-load current" rating. That is simply the nameplate rating of the Xformer in VA, (volt-amps) or KVA (1000Volt-amps) for larger Xformers. Simply divide the nameplate rating in VA or KVA by the supply voltage and you'll get the Xformers potential maximum output in ampheres.
How many percent will be the starting current for motor?
Motor starting current is typically 5-7 times the rated current of the motor. (For three phase induction motors)
What is the condition at which torque developed in 3 phase induction motor is maximum?
sadasd
How does mpcb work?
The basic working principle is similar to all other circuit breakers.• Thermal protection is used to guard the electric motor against overload. It is based on an expanding and contracting contact that disconnects the motor if excessive current is detected. It is very important to know that thermal protection has a delayed response, to allow the high inrush currents when a motor starts. However, if the motor is unable to start for some reason, thermal protection will trip in response to the extended inrush current.• Magnetic protection is used when there is a short circuit, line fault, or other high current electric fault. Unlike thermal protection, magnetic protection is instantaneous, to immediately disconnect the dangerous fault currents.• The main difference between the MPCB and other circuit breakers is that the MPCB can provide protection against phase unbalance and phase loss. Three-phase circuit motors require three live conductors with balanced voltages in order to operate effectively. An unbalance of more than 2% will be detrimental to the motor's service life. If one of the phase voltages is suddenly lost, the effect is even more damaging because the motor will keep on running with only two phases. The motor protection circuit breaker is capable of detecting these conditions by measuring the differences among phase voltages, and disconnects the motor immediately when they occur. It is important to note that phase current unbalance is normal in three-phase systems that power separate single-phase loads, but is unacceptable when the three-phase circuit powers an electric motor.• MPCBs are also equipped with a manual interruption mechanism, allowing disconnection of electric motors for replacement or maintenance.Motor protection circuit breakers are available in a wide variety of current ratings, and one of their best features is that many models allow the current rating to be adjusted. This means that the same MCPB can be configured to protect motors of different capacities.
What should be the current of siemens 75 kw motor at no load?
starting current of 3 phase 75 KW induction motor
What would be the horse power required in a 3-phase motor to replace a .5 horsepower single phase motor.?
You still need the same horsepower. The advantage of the three-phase motor is that it will draw lower current.
