# Voltage frequency relationship formula 1

### Alternating current - Wikipedia

For Higher Physics revise how to determine peak voltage and frequency from oscilloscope This relationship is shown by the equation f= \frac {1}{T}. Frequency. The setup measures the voltage in terms of frequency and can 1) with a very low nonlinearity error of % at 10 kHz, % at kHz. 1 Volts per hertz ratio; 2 Constant torque load; 3 Constant horsepower load; 4 Reduced voltage and frequency starting; 5 Selecting a motor.

If you have an alternating current power source, the voltage and current can change from one instant to the next.

OK, let me try to say a little more about it, in informal terms. On the one hand, suppose you have a big powerful battery, like a volt car battery.

## Monitoring and measuring a.c.

It wants to supply direct current DC - its frequency is zero 0. Now you connect an incandescent automobile light bulb to it of, say, watts a really bright bulb. For that light bulb to dissipate watts of power, at 12 volts, it has to draw 10 amps of current.

Now, reverse the battery connections to the bulb. It still is as bright as before, still dissipates w.

The difference is, the voltage across the bulb is the opposite of what it was before, and the current is the opposite also, but when they are multiplied, the power is still positive. Suppose you reverse the connections 60 times per second, or, or a million.

### Alternating current motor drives -

How much power does the light bulb dissipate? The same, because there is no time when V times I is not equal to w.

Some examples of constant torque loads are: Such applications need less torque at higher speeds, yet require voltage to be no higher than the rated nameplate voltage because the motor insulation deteriorates exponentially at higher-than-rated voltage. Because the motor horsepower is directly proportional to the torque and speed of the motor, it remains constant while torque decreases in proportion to the increase in frequency.

As such, a motor that is operated above its rated frequency is operating in a region known as constant horsepower see Fig. The drive starts and accelerates the motor smoothly as frequency and voltage are gradually increased to the desired speed.

Which is the Killer, Current or Voltage?

A load that needs more starting torque than a drive can deliver requires a drive with a higher current rating. It is appropriate to supply a drive with a higher continuous horsepower rating than the motor when high peak torque is required.

Selecting a motor AC drives often have more capability than the motor. Drives can run at higher frequencies than might be suitable for an application. Drives also can run at lower speeds than might be suitable. For example, a self-cooled motor might not develop enough air flow for cooling at reduced speeds and full load. Each motor must be evaluated according to its own capability before selecting it for use on an AC drive.

Harmonics, voltage spikes, and voltage rise times of AC drives are not identical. Some AC drives have more sophisticated filters and other components that are designed to minimize undesirable heating and insulation damage to the motor.