14
0%
25%
50%
75%
100%
100%75%50%25%0%
% SPEED
% TORQUE
% HORSEPOWER
% FLOW
“Variable torque” refers to the fact that the torque required varies with the square
of the speed. Also, the horsepower required varies with the cube of the speed,
resulting in a large reduction in horsepower for even a small reduction in speed. It
is easily seen that substantial energy savings can be achieved by reducing the
speed of a fan or pump. For example, reducing the speed to 50% results in a 50 HP
motor having to produce only 12.5% of rated horsepower, or 6.25 HP. Variable
torque drives usually have a low overload capacity (110% - 120% for 60 seconds),
because variable torque applications rarely experience overload conditions. To
optimize efficiency and energy savings, variable torque drives are usually
programmed to follow a variable V/Hz ratio.
The term “constant torque” is not entirely accurate in terms of the actual torque
required for an application. Many constant torque applications have reciprocating
loads, such as vibrating conveyors and punch presses, where the rotational motion
of the motor is being converted to a linear motion. In such cases, the torque
required can vary greatly at different points in the cycle. For constant torque
loads, this fluctuation in torque is not a direct function of speed, as it is with a
variable torque load. As a result, constant torque drives typically have a high
overload rating (150% for 60 seconds) in order to handle the higher peak torque
demands. To achieve maximum torque, constant torque drives follow a constant
V/Hz ratio.
Both MC Series product lines (MC1000 and MC3000) have full overload capacity
(150% for 60 seconds, 180% for 30 seconds), so that either one can be used for
either type of application. The V/Hz ratio can also be changed to optimize
performance for either type of application.
6.2 DRIVE FUNCTION DESCRIPTION
The MC Series is a 16 bit microprocessor based, keypad programmable, variable
speed AC motor drive. There are four major sections: an input diode bridge and
filter, a power board, a control board, and an output intelligent power module.
To Next Page
Loading...
Need help?
General
