What is short time rating of motor?

A short time rating of an electric motor can be defined as the extrapolated overload rating of the motor which it can supply for the specified short time without getting overheated. Now a days the machines are being designed and manufactured for short duration having sufficient overload torque capability.

What is short time duty motor?

#2 Short Time Duty (S2)

The second type of motor duty cycle is short time duty. Similar to continuous duty, this operation runs with a constant load. Unlike continuous duty, it is shut off before it reaches thermal equilibrium. The motor is then allowed to rest long enough for it to reach ambient temperature.

What do you mean by short time duty?

The short time duty (or short time operation) indicates an operating mode of increased performance but for a shorter length of time. Commonly it is also referred to the maximum load (the performance) at which and the related maximum length of time a device can be operated without to failure.

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What is SF on a motor?

The service factor – SF – is a measure of periodically overload capacity at which a motor can operate without damage. … A motor operating continuously at a service factor greater than 1 will have a reduced life expectancy compared to operating at at its rated nameplate horsepower.

What does TE on a motor mean?

The tight enclosure prevents the free exchange of air but potential contamination entering through the shaft limits these motors to indoor/outdoor applications that do not allow for hazardous, corrosive, or explosive damage. ODP: Open Drip Proof.

Which is an example of short time duty?

Short Time Duty (Fig.

Some examples are: crane drives, drives for household appliances, turning bridges, sluice-gate drives, valve drives, and many machine tool drives for position control.

What is intermittent duty and short time?

Short time loads: The load of the motor occurs periodically remains constant for short time and then remains idle for longer time. Short time intermittent loads: The load on the motor occurs periodically in identical duty cycle, each duty cycle having period of application of load and rest.

What is short time rating?

An electric machine rating which allows for cooling between working periods resulting in a rate higher than the cmr value. The rating-plate shows a designation of either 1h or 1/2h which is the time the machine can operate under rated conditions starting from ambient temperature. S.

What is mean by short time rating of motor?

A short time rating of an electric motor can be defined as the extrapolated overload rating of the motor which it can supply for the specified short time without getting overheated. Now a days the machines are being designed and manufactured for short duration having sufficient overload torque capability.

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Can a motor of smaller rating be selected for short time duty?

The short-time duty motor operates at a constant load for some specified periods which is then followed by a period of rest. … Thus a motor of smaller rating can be operated with a larger power output for the maximum temperature rise in a short duration.

What is the SF rating on a motor?

Service factor — Service factor (SF) is an indication of how much overload a motor can withstand when operating normally within the correct voltage tolerances. For example, the standard SF for open drip-proof (ODP) motors is 1.15.

What is SF hp?

Permissible horsepower loading. Motor Service Factor (SF) is the percentage of overloading the motor can handle for short periods when operating normally within the correct voltage tolerances. … This means that a 10-hp motor with a 1.15 SF could provide 11.5 hp when required for short-term use.

What does SF Max Amps mean?

Service Factor is defined as a motor’s ability to operate under a short-term load. The higher a motor’s S.F. rating is, the more durable the motor. Motors with a high S.F. … Full Load Amps, or F.L.A., represents the amount of current the motor is designed to draw at the rated horsepower.

What is the tE time of an electric motor?

Time ‘tE’ is the locked rotor withstand time. It is the time taken for heating up any part of the motor from the steady state temperature up to the limiting temperature under the locked rotor condition. This time is determined separately for stator and rotor and the minimum one is taken as the tE.

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How do you read a motor rating plate?

The RPM listed on the nameplate is the shaft speed for the motor. The speed of the motor is directly related to the frequency of the line voltage and the number of poles in the motor. At 60 Hz, a 4 pole motor will rotate at approximately 1800 RPM (7200/4 poles).

What is IA in in motor?

IA/IN ratio is the ratio of starting current to rated current of Ex e motor and it should not be more than 10 [2]. … The time tE of increased safety motor can be increased either by increasing rotor bar mass or by reducing starting current and or increasing stator coil pitch.