Electric motors have a very large amperage. Finding the right breakers and fuses for a motor, whether it’s a small electric motor or an industrial one, must be calculated carefully. The wrong breakers and fuses may cause failure and overheat. Low voltage can also cause failure. 

When the circuit breaker or fuse is the right size, you can test the voltage. Ideally, the voltage at the end of the wire and the starting load requirements will be the same. Simply hook the small or large electric motor to the ends of the wire. Turn it on. What does the voltage do? Is it dropping? Does it stay the same? If the voltage drops, then your wires are too small for the motor.

Chart of Common Wire Resistance

Ideally, the motor has a fuse with an important time-delay somewhere between 175-250% of the motor’s full load operating amperage. This depends on whether or not you use a circuit breaker. The chart below is a general guide to help you choose the right wire. Always talk with a professional when finding the right wires you need.

*ohms/1000 ft


























Additionally, you might need to increase the wire if the voltage drop is too significant. The wire needs to carry 25% more amperage than the motor draws at maximum full-load operation.

Choosing the Right Fuse

The fuse breaks the circuit when the current is too high. Do you know the full-load-steady-state current when at 25 degrees Celsius? You need to know that number to calculate the right fuse. Ideally, your fuse rating should be 135% of that value. Look at the power of your appliance or motor and the voltage. There are many types of fuses:

  • Cartridge Fuse
  • Rewireable Fuse
  • Switch Fuse
  • Drop Out Fuse
  • MOV Fuse
  • Resettable/POLYFUSE
  • Automotive Fuse
  • Expulsion Fuse

Always round up the rating after doing necessary calculations, or just call us at LN Electric. We will be happy to help you calculate the right fuse for your needs.

Should I use a Fuse or Circuit Breaker?

Your circuit breakers play a vital role in the primary electricity distribution system. Unfortunately, the simple fuse many times only handles a certain amount of amperage. This depends entirely on its rating. On the other hand, a circuit breaker can be reset safely if tripped. Most homeowners use circuit breakers instead of fuses in their homes. The fuse tends to melt when overheated. Being able to re-use the circuit breaker is the primary advantage.

Call the Professionals at LN Electric Motor

Choose the correct breaker or fuse for your motor every time. Selecting the wrong part can result in severe damage, failure, and even personal injury or property damage. Call the experts at LN Electric today. When you need to find the right motor, our impressive inventory has the solution you need.

Our friendly staff will be happy to find you the right products. Leaders in the field, LN Electric has decades of experience and excellent customer service. We are dedicated to helping our clients find what they need every time, and at an affordable price. Contact us today.

Call (416) 661-5667