How Many Amos For 20 HP Squirrel Cage Motor?
The following information pertains to three-phase squirrel cage induction motors. These motors are most often used to drive hydraulic pumps. Using the full load amps on the motor’s nameplate as your final calculation, you should use a fuse of the next higher size. If the size you calculated does not match the standard size, you should use a fuse of the next larger size.
204 amperes is not a standard size
The 204 amperes standard for a 20 hp squirrel cage motor is not enough to protect your motor against overheating. You must use three #8 THHN conductors, each sized at 1/8 of an inch. Then, you must connect the squirrel-cage induction motor to its rated line voltage. Similarly, a molded case switch must be a listed device and must have a motor-circuit switch with a rated horsepower.
The fuses used in a feeder circuit should be rated at 150 percent of the full-load current of the motor. The next-larger-size fuse is two-hundred-and-fourty-amp nontime-delay fuses. These fuses must be sized in accordance with the provisions of the Code. When a 20-hp squirrel cage motor is protected with a 100-amp fuse, an electrician may choose a smaller size.
Table 430-152 shows branch-circuit short-circuit protection and ground-fault protection. In addition, a motor circuit overcurrent device shall not exceed 300 percent of the full-load current of the motor. The table also contains values for protective devices for motors, but these do not correspond to standard sizes. In this case, you should use the next-larger-size device.
Using full load amps of the motor nameplate for final calculations
When you calculate the full load amps of a motor, you are not using a calculation tool, but the actual nameplate values. Using the nameplate amps is a great way to make sure that the motor is sized correctly and that it will run properly. This is the current rating that is used for setting adjustable OL relays and soft starters, among other things.
To determine the full load amps, you need to know the nameplate amperage for your motor. If the nameplate does not have this information, you can look up the actual power. The full load amps are indicated on the motor nameplate, while a blank number indicates that the motor is not rated for a certain amount of current. The code letter is often used to represent the mid-range inrush current.
You can also use the full load amps of three-phase motors. The nameplate information will include the full load amps of three-phase motors. In three-phase systems, it is possible to use either a delta or star connection, as long as you know the exact ratio of the two voltages. When choosing switchgear, use the full load amps of the motor nameplate as a reference.
Using a fuse of the next higher size if the calculated size isn’t a standard size
If you calculate the current drawn by an electrical circuit, you should use the maximum fuse rating. If the size calculated doesn’t match a standard size, you can use a fuse of the next higher size. In most cases, a fuse of the next higher size is perfectly safe. For example, if you’re running an amplifier in parallel with a wire segment “D”, you’d use a fuse rated at 50 amps. The fuse holder would have a second secondary AGU holder that was equipped with a 7.5 amp fuse.
You can use a push-on speaker terminal as a makeshift fuse holder. Simply push the fuse terminals together with a wire tie or tape. To protect your wires, you can also use electrical tape. This will keep your hands from coming into contact with the fuse terminals. Once you’ve disconnected the wires, you can now install the new fuse.
The next higher standard size fuse for a motor circuit is 84 amperes. If the calculation doesn’t match the fuse size, you can use a time-delay cartridge fuse. Then, you can use a 240-62 table to find the right size and color for your electrical system. To find the right size, you can divide the calculated ampage by 175%. Then, pick a number in the middle of the range. You can also refer to a chart published by Littelfuse that provides information about the various sizes.
Jessica Watson is a PHD holder from the University of Washington. She studied behavior and interaction between squirrels and has presented her research in several wildlife conferences including TWS Annual Conference in Winnipeg.