# What is the relationship between voltage and generator shaft speed

### AC Generator Theory | AC Electric Circuits Worksheets

Describe the factors influencing the magnitude of the voltage induced by motion, and . This relationship between flux and induced voltage is expressed in does an alternator have if it generates Hz power at a shaft speed of RPM?. When not connected to a load resistance, generators will generate voltage roughly proportional to shaft speed. With precise construction and design, generators. Output voltage of the generator is controlled by changing the strength of the . Governors control generator shaft speed Electrical Connection.

**Electric Motors: "AC Motors and Generators" 1961 US Army Training Film TF9-3107**

In our example input electrical power of the motor is 0. Motor torque changes with the speed.

### Generator speed, and power output. Frequency - Electrical Engineering Stack Exchange

At no load you have maximum speed and zero torque. Load adds mechanical resistance.

The motor starts to consume more current to overcome this resistance and the speed decreases. If you increase the load at some point motor stops this is called stall. When it occurs the torque is at maximum and it is called stall torque. While it is hard to measure stall torque without special tools you can find this value by plotting speed-torque graph. You need to take at least two measurements with different loads to find the stall torque.

How accurate is the torque calculation?

## Tachogenerators

While voltage, current and speed could be accurately measured, efficiency of the motor may not be correct. Hide answer Challenge question: Note that the two wire ends switch polarity as the loop rotates.

Ask your students to explain why the polarities are as they are. What factors determine the magnitude of this voltage? Is the induced voltage AC or DC? How can you tell?

- AC Generator Theory

AC generators, or alternators as they are sometimes called, are typically long-lived machines when operated under proper conditions. But like all machines, they will eventually fail.

It must be suitably sized for current as the battery ESR determines the max current to raise the voltage to The biggest load is a an undercharged battery. When batteries age each cell becomes more mismatched and the weakest cell can boil the electrolyte from over voltage from excess alternator current to reach So installing a bigger alternator on an old battery, can result in battery failure quicker than normal.

## Calculations

Also as diode bridges get hotter and age slightly with higher ESR a fresh battery with higher CCA rating and lower ESR result can increase the stress on the alternator bridge and fry it in ar least one phase so the alternator reduces its capacity from 3 phase to 2 or 1 phase and can no longer keep up to worst case load current causing the headlamps to dim at normal idle. This means the ESR is So what is the max current to raise the battery from 12 V undercharged to Again from Ohm's Law, Fortunately the diodes can handle brief over current periods and the weak alternator could fry its diodeswhile a stronger one might need more RPM to raise the voltage to Thus the alternator current and battery CCA are designed for each vehicle to increase longevity at the least cost by careful selection of matching diode ESR and battery cell ESR mismatch from aging.

This is why they sometimes dont last long after replacing one or the other. This is aggrevated by excessive V regulator settings and poorly sized or maintained batteries.