Rockwell Automation SP500 AC Drive Installation and Operation Manual - Manual (Page 16)

2-2 SP500 AC Drive Installation and Operation Manual Version 3.1
• User-selectable relay contact for indications of drive running, drive faulted, or drive
at selected speed
• User-selectable power-up start, auto-restart, and coast-to-rest or ramp-to-rest stop
functions
• User-selectable local or remote operation
• 29 user-adjustable software parameters
2.2 Drive Description
The SP500 drive is an AC PWM (pulse-width-modulated) inverter that operates on
single- or three-phase power. See figures 2.1 and 2.2. AC input power is applied to the
drive’s input terminals. Voltage transients are suppressed by three
metal-oxide-varistor (MOV) suppressors. These suppressors keep any input voltage
transients within the maximum voltage rating of the input diode module.
The input diode module rectifies the incoming AC voltage into a constant DC bus
voltage which is filtered by the DC bus capacitor bank. An internal DC-to-DC power
supply uses power from the DC bus and provides the necessary voltages required by
the drive. Under regulator software control, the IGBT (insulated-gate
bipolar-transistor) inverter bridge converts the constant DC voltage into an AC PWM
waveform. The regulator switches the IGBT inverter bridge using a 4, 6, or 8 kHz
carrier frequency (user-selectable). A low carrier frequency maximizes the power
rating of the drive but also increases acoustic noise. A high carrier frequency selection
reduces acoustic noise but results in a derating of the drive’s efficiency.
The volts per hertz (V/Hz) regulator governs the open-loop operation of the drive for
adjustable-speed performance of AC induction and synchronous motors. The
regulator maintains a ratio of voltage to output frequency that provides constant or
variable torque across a wide speed range. Drive operation can be adjusted by the
parameters entered through the keypad. A microprocessor on the Regulator board
controls drive regulation. See figure 2.3. The Regulator board accepts internal power
feedback signals and an external speed reference signal. The Regulator board
provides display data for a four-character display, which is used to indicate drive
parameters, parameter values, and fault codes.
The drive can be controlled either locally through the keyboard and display (see
section 7) or remotely through the terminal strip (see section 5).
The drive is intended to operate trip-free under any condition. The drive uses selected
signals to extend the acceleration (starting) and deceleration (stopping) rates of the
motor when an overcurrent condition occurs. When a fault does occur, however, the
regulator generates an instantaneous electronic trip (IET) signal to turn the drive off
(coast-to-rest). The drive stores an indication or record of the IET fault, which can be
viewed on the four-character display. After a fault, the STOP/RESET key or a
user-supplied IET RESET pushbutton must be pressed to reset the IET signal and
clear the fault from the drive.