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Drive Variable

Why use a variable frequency drive along with an electric motor?

The three most important reasons are:-
1. Allows a wide range of speed control.
2. May be more economical and reliable than the alternatives.
2. Allows much HIGHER shaft speed than available using mains frequency.
. How is this?

. Motor rotating magnetic field RPM
= Frequency of applied voltage x 60 / No of pairs of poles.

. This shows max RPM occours with one pair of poles.
There cannot be less than one pair.
. The 60 converts RPSec to RPM.
Mains frequency is fixed at 60Hz for USA, 50Hz Europe.
. When a 50Hz supply is connected to a motor,
with one pair of poles, then the rotating field RPM
= 50 x 60 / 1 = 3000 RPM.
This the motors max speed!

The actual rotor or shaft RPM, will be about 3.5% less than this, due to necessary slip.
Modern woodworking cutters run in excess of 24,000 RPM.
What frequency is required to run a two pole motor at this speed?
Note two pole = one pair of poles.
Re-arranging; Freq
= Field RPM x Pole pairs / 60
= 24,000 x 1 /60 = 400 Hz.
Much aircraft equipment requires a 400Hz AC supply.
Electronic circuits can easily convert 50Hz/60Hz mains
to any other higher or lower frequency.

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600 HP 460V TECO VARIABLE FREQUENCY DRIVE EQ5 4800 C    US $45,180.00

500 HP 460V TECO VARIABLE FREQUENCY DRIVE EQ5 4700 C    US $41,445.00

450 HP 460V TECO VARIABLE FREQUENCY DRIVE EQ5 4600 C    US $36,330.00

400 HP 460V TECO VARIABLE FREQUENCY DRIVE EQ5 4500 C    US $33,300.00

400HP 460V Mitsubishi Variable Frequency Drive New    US $31,839.00

Robicon Siemens 800hp VFD Variable Frequency Drive 575V    US $25,000.00

Robicon Variable Frequency Drive 4160 VAC 500 HP NEW    US $20,000.00

350 HP Omron Variable Frequency Drive FREE SHIPPING    US $19,720.00

350 HP 460V TECO VARIABLE FREQUENCY DRIVE EQ5 4450 C    US $19,120.00

500HP 460V VARIABLE FREQUENCY DRIVE IRRIGATION FAN DUTY    US $17,813.00

350 HP 460V TECO VARIABLE FREQUENCY DRIVE EQ5 4400 C    US $16,410.00

300 HP 460V TECO VARIABLE FREQUENCY DRIVE EQ5 4350 C    US $15,835.00

200HP 480V Mitsubishi Variable Frequency Drive New    US $15,701.00

400HP 460V VARIABLE FREQUENCY DRIVE IRRIGATION FAN DUTY    US $14,600.00

350HP 460V VARIABLE FREQUENCY DRIVE IRRIGATION FAN DUTY    US $13,425.00

250 HP 460V TECO VARIABLE FREQUENCY DRIVE EQ5 4300 C    US $12,699.00

300HP 460V Mitsubishi Variable Frequency Drive New    US $12,642.00

100HP 460V Mitsubishi Variable Frequency Drive New    US $11,808.00

200 HP 460V TECO VARIABLE FREQUENCY DRIVE EQ5 4250 C    US $11,400.00

125 HP 230V TECO VARIABLE FREQUENCY DRIVE EQ5 2150 C    US $11,285.00

250HP 460V Mitsubishi Variable Frequency Drive New    US $10,830.00

200HP 460V Mitsubishi Variable Frequency Drive New    US $10,046.00

300HP 460V VARIABLE FREQUENCY DRIVE IRRIGATION FAN DUTY    US $10,025.00

VFD VARIABLE FREQUENCY DRIVE YASKAWA F7 F7U 200HP300HP    US $9,900.00

75HP 460V Mitsubishi Variable Frequency Drive New    US $8,949.00

150HP 460V Mitsubishi Variable Frequency Drive New    US $8,938.00

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