Electric Motor Fuse Sizing Chart

B best protection is obtained by measuring motor running.

Electric motor fuse sizing chart.

If motor running protection will be provided by the fuses select fuse ratings for correct type of motor from motor protection table columns headed without overload relays. Circuit breaker size and amps charts. This fuse sizing is normally large enough to allow the. The largest size fuse shown in the chart is the 5ag or midget a name adopted from its use by the electrical industry and the national electrical code range which normally recognizes fuses of 9 16 x 2 as the smallest standard fuse in use.

Yet for many cases this fuse amp rating selection is smaller than the maximums allowed per columns 5 or 6 430 52. For motors it is recommended to multiply the nameplate fla by 1 25 for wire sizing. In some cases this smaller amp rating. Motor full load amps are taken from motors currently used by champion.

Below is the given chart showing the of max current rating of breaker size for different types of load currents. 8 branch circuit fuse size individual motor load with fuse overload protection no starter overload relays. Chart to determine fuse breaker and wire sizes for electric motors for single phase a c. The following table gives wire breaker and fuse sizes based on horsepower voltage and phase.

Select motor size from horsepower column making certain you are in the correct voltage. A motors with 1 15 service factor or temperature rise not over 40 degrees c size fuses at not more than 125 of the motor nameplate current rating. Fuse ratings for motors with special characteristics may need to vary from given values. The maximum safe current limit is 80 of the rated size of breaker except some motors.

Fuses sized in accordance with column 4 must be used in conjunction with properly sized motor overload protection such as overload relays or solid state motor controllers 430 32. Amperes enter the maximum current in amps that will flow through the circuit. Fuses open the circuit quickly in case of a massive overload or short circuit. Motors are usually protected by both fuses or circuit breakers and by heater coils in a magnetic starter.

Voltage enter the voltage at the source of the circuit. The wire breaker and fuse sizes are provided as a reference for the installer and are based on the 1996 national electrical code. 430 250 covering standard speed ac motors with normal torque characteristics. Single phase voltages are usually 115v or 120v while three phase voltages are typically 208v 230v or 480v.

This fuse sizing is normally large enough to allow the overload protective device to operate on overloads without opening the fuse. Tection for motor branch circuits 430 52 but typically are not the maximum allowed. Select fuse or breaker size from column 3 or 4.