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Why must electrical motor need overload protective device?
mane lak tau
What is overload protection?
It is protection installed to protect, usually motors, from going beyond the amperage capacities that were set down by the manufacturer's specifications of the motor. As a motor loads up to its rated HP it will operate within the motors amperage range. More loading on the motor will increase the amperage draw to a point where the motor's winding will start to burn or short out due to insulation breakdown of the motor coils. Over load protection is a settable device that will limit the current to a specific value. The setting on the over current device is the motor's FLA (full load amps). If the motor amperage goes higher that the set point the overload protection, the overload protection contacts will open and drop the motor's magnetic contactor off line. In some cases this could be an annoyance but it does save the motor from destroying itself.
What is efffect of load on motors?
As the load increases on a motor the amperage rises. Increasing the load amps over the motors full load amp rating can shorten the motor's life because of excessive heat. Motors should have overload protection in their circuits to prevent this condition from happening by tripping the motor contactor and opening the motor's voltage supply. <<>> Gets very warm .... vibrations., possible melt, seize, much energy expended.
What are advantages of 200V 3ph motor over 380V 3ph?
In most applications 200v is easier to get for a supply voltage than 380v.
Could over-current be caused by low voltage?
No, not directly. The supply voltage has to rise or the resistance has to fall to get over-current. If there was a secondary control voltage that was part of a voltage control circuit for a higher voltage, it is conceivable that a voltage drop in control circuit could cause an over-voltage in the supply. Motors are constant power devices, so this could be true for a motor. If you have a 1hp motor (loaded at 1hp), it will want to draw 1hp of power no matter the supply voltage. If the voltage dips, the motor will require more current to keep it spinning at it's normal speed.
What does a protection diode do?
It will conduct electricity when the voltage across its terminals reaches a certain value. Once the over voltage is extinguished, the protection diode becomes an open circuit again. Therefore, you need to connect a protection diode between both wires to be protected (differential mode) and from each wire to ground (common mode). Protection diodes are primary protection devices (fast reacting), but they cannot handle too much current. That is why they need to be used with secondary protection devices (fuses and gas arrestors) to provide better protection.
Why must electrical motor need overload protective device?
mane lak tau
What is the difference between voltage restrained overcurrent protection and voltage controlled overcurrent protection?
The voltage-restrained overcurrent relay adjusts the pickup setting and characteristic curve of the overcurrent function based on the system voltage. The relay is set pickup greater than overload, and sensitivity increases as the voltage drops. The voltage-controlled overcurrent relay uses an undervoltage element to supervise the operation of the overcurrent element. When the voltage drops below a predetermined level, the undervoltage element permits the operation of the time overcurrent units. Voltage-restrained overcurrent relays can provide faster backup protection than voltagecontrolled overcurrent relays, particularly in cases where the generator voltage does not drop significantly below rated voltage during fault conditions. If the generator voltage always drops below a given voltage level for all faults in which operation is required, the voltage-controlled overcurrent unit may be set to provide faster overall clearing speed
What is phase failure relay?
These relay sense the Negative Sequence Voltage components of system supply & offers protection against Phase Failure, Phase Sequence Reversal with Under/Over Voltage conditions which are dangerous to motor winding and cause motor burnouts.
What is a mcb and what is it used for?
mcb is master circuit breaker. it is used in the circuit for the protection of equipments from over voltage.
How to control motor rpm?
For AC motor, you can change motor RPM by changing its supply voltage or by changing supply frequency. For DC motor, you can change motor speed by controlling armatyre voltage or field current.
What is power cable size for 1 kw 1 phase motor over 500 meters?
It depends on the voltage that the motor needs, because a higher voltage requires less current for a given amount of power. Also a higher voltage can tolerate a higher voltage drop. So there are two things that lead to a thinner wire when the voltage is higher.
Can a numerical relay give protevtion to over current over voltage and short circuit current at the same time?
Yes. Most microprocessor based relays that have both voltage and current inputs can provide overcurrent and over voltage protection simultaneously. Short circuit current is the same as overcurrent.
When do pedestrians have the right away over motor vehiclas?
pedestrians have lower protection over motor vehicles therefor they must enter and leave an intersection faster, giving them the right of way over vehicles
What size wire should be use for connecting a 110 kw motor over a distance of 108 meters?
This is a voltage drop question. To answer this question a voltage must be given.
What is overload protection?
It is protection installed to protect, usually motors, from going beyond the amperage capacities that were set down by the manufacturer's specifications of the motor. As a motor loads up to its rated HP it will operate within the motors amperage range. More loading on the motor will increase the amperage draw to a point where the motor's winding will start to burn or short out due to insulation breakdown of the motor coils. Over load protection is a settable device that will limit the current to a specific value. The setting on the over current device is the motor's FLA (full load amps). If the motor amperage goes higher that the set point the overload protection, the overload protection contacts will open and drop the motor's magnetic contactor off line. In some cases this could be an annoyance but it does save the motor from destroying itself.
What is efffect of load on motors?
As the load increases on a motor the amperage rises. Increasing the load amps over the motors full load amp rating can shorten the motor's life because of excessive heat. Motors should have overload protection in their circuits to prevent this condition from happening by tripping the motor contactor and opening the motor's voltage supply. <<>> Gets very warm .... vibrations., possible melt, seize, much energy expended.
