Motor Circuit Protector Sizing Chart

Time delay fuse ratings may be increased to 225 and non time delay fuse ratings to 400 300 if over 600 amperes if the ratings.

Motor circuit protector sizing chart.

A good field reference for maintenance and troubleshooting is ugly s electric motor and controls ugly s electric motors and controls 2014 edition this calculator is based on information found in this reference guide and can help electricians troubleshoot maintenance and control circuits. Short circuit protection the motor branch circuit fuses may be sized as large as shown in table 2 when an overload relay or motor thermal protector is included in the branch circuit. Other means such as overload relays provide the motor overload protection. The first is to protect the cable supplying the motor the power source and any components upstream on the circuit from the motor.

Selecting fuses for motor running protection. Motor protection uide using ac motor protection tables to select fuse ratings time delay rk1 and rk5 fuse ratings selected in accordance with the following recommendations also meet nec motor service requirements for motor branch circuit and short circuit protection. Locate where your motor falls in table 430 52 based on the full load current and motor size. Motor circuit protectors hmcp eaton s motor circuit protectors are ul recognized instantaneous only breakers for motor short circuit protection.

For motor circuit conductors tapped from a feeder 430 28 determine the ampacity per 430 22. The fuse sizing in column 4 for lps rk sp lpn rk sp frs r and frn r fuses provides a degree of motor and circuit overload protection to back up the normal motor overload protective device. Protection against electrical faults such as short circuits line to ground faults and line to line faults. The table will give you the size of the short circuit protection as a percentage of the full load current.

Circuit breakers which are called mcps or motor circuit protectors are sized with the intent to provide only short circuit and ground fault protection for the motor branch circuit protection per 430 52. This level of protection requires a well designed true dual element fuse. This table is used to size the short circuit protection check the motor data sheets for the motor s full load current. Typical thermal magnetic circuit.

There are typically two different sets of protections to design for when designing motor circuits. This is called circuit protection or feeder protection. The next size up protection rule for branch circuits 430 52 c 1 ex 1 doesn t apply to motor feeder short circuit and ground fault protection device sizing. The mpcb can interrupt any electrical fault that is.