Ok, we know that an electric motor needs to be rated 2x as much as it's usage for long life, so with 3000W I will get to use 1500W. Therefore, I am wondering how to interpret the government rule below. According to their specs, is there a limit to what size my electric motor can be? The way it is worded, it sounds like the gross BHP only applies to the motor with auto transmission.....but I would like to know what others think when they read it.
{a "motorized tricycle" is a three-wheeled device, designed to carry not more than two persons, including the driver, and having either an electric motor or
a motor with an automatic transmission developing less than two gross brake horsepower
and capable of propelling the device at a maximum speed of not more than 30 miles per hour on level ground.}
{a "motorized tricycle" is a three-wheeled device, designed to carry not more than two persons, including the driver, and having either an electric motor or
a motor with an automatic transmission developing less than two gross brake horsepower
and capable of propelling the device at a maximum speed of not more than 30 miles per hour on level ground.}
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BHP or Brake Horse Power means power developed at the drive wheel. It is measured using a dynamometer, which is the equivalent of applying a brake to the wheel (hence the name BHP) using a generator as a load. If your prototype vehicle had to be tested for some certification reason, that's the type of test that would be done. So the requirement effectively applies to both an engine and an electric motor, but does allow each to be oversized enough to overcome transmission losses.
A service factor of x2 on an electric motor sounds excessive. If it were an AC motor, a service factor of 1.15 would be ample. If you really want to use a 3kW motor (about 4HP) instead of 1.5kW motor (about 2HP) then ask the manufacturer to mark the nameplate of the 3kW motor as Full Load 1.5kW, Service Factor 2.0, and set the overload ratings for a 1.5kW motor. Then you'll have your excessively long-life motor but will meet regulatory requirements and be capable of passing the dynamometer test.
Another way to ensure long life is to stick with a 1.5kW motor, but have the manufacturer wind it with a higher-temperature-class insulation system. It is temperature rise that causes motors to eventually wear out. By using insulation components that can withstand higher temperatures, the actual operating temperatures become a lesser percentage of the maximum allowable temperatures, and the motor life is extended exponentially.
A service factor of x2 on an electric motor sounds excessive. If it were an AC motor, a service factor of 1.15 would be ample. If you really want to use a 3kW motor (about 4HP) instead of 1.5kW motor (about 2HP) then ask the manufacturer to mark the nameplate of the 3kW motor as Full Load 1.5kW, Service Factor 2.0, and set the overload ratings for a 1.5kW motor. Then you'll have your excessively long-life motor but will meet regulatory requirements and be capable of passing the dynamometer test.
Another way to ensure long life is to stick with a 1.5kW motor, but have the manufacturer wind it with a higher-temperature-class insulation system. It is temperature rise that causes motors to eventually wear out. By using insulation components that can withstand higher temperatures, the actual operating temperatures become a lesser percentage of the maximum allowable temperatures, and the motor life is extended exponentially.