inverter drive great help

P

Thread Starter

pascal

please i need your help!!!

i have a variable speed drive which is driving my induction motor, which in turn is connected to a centrifugal pump. i want to know if:

1) the ratio of voltage supply to frequency is constant?

2) the developped torque in the motor is it constant or a variable one?

3) is the ratio voltage supply to frequency always constant?

please i really need this information.

thank you
 
1) Voltage to Frequency ratio will remain constant up to the base frequency. in other words if you are not over speeding the motor as you increase the frequency output to the motor (to increase speed) the voltage will increase proportionaly. I know some drives like the Reliance GV3000 have the ability to provide different V/f curves i.e linear, squared (for pumps), etc.

2) from what I understant in centrifugal pumps the developed torque is variable.

3) The V/f is only constant up to base speed after base speed has been reached the voltage can no longer increase (limitation of the motor).

Hope this helps.
 
W

William Sturm

> i have a variable speed drive which is driving my
> induction motor, which in turn is connected to a
> centrifugal pump. i want to know if:
>
> 1) the ratio of voltage supply to frequency is
> constant? <

Yes, ususally.

> 2) the developped torque in the motor is it constant
> or a variable one? <

Can be either, ususally can be configured in the
inverter.

> 3) is the ratio voltage supply to frequency always
> constant? <

Up to the motors base speed, the V/F ratio is
typically constant. However, it can usually be
modified slightly for low speed torque boost.

Bill Sturm
 
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