Allen-Bradley PowerFlex 755 Quick Start

64 Rockwell Automation Publication 750-QS001A-EN-P - March 2015
Reference Section
A 3-wire control circuit consists of a normally closed stop button (STOP), a normally open start button (START), and
sealing contact (M), and the coil of a magnetic motor starter. When the normally open start button is pressed, the coil of
the magnetic motor starter is energized. An auxiliary contact seals around the start button to provide a latched circuit. In
the case of a VFD, the internal logic control of the VFD functions identical in principle to the sealing contact.
Pressing the normally closed stop button disrupts the circuit. The 3-wire control circuit provides what is known as “low-
vo
ltage protection.” In the event of a power failure, the magnetic motor starter drops out. In this case, however, when power
is restored the magnetic motor starter does not automatically reenergize. The operator must press the start button to
initiate the sequence of operations.
The 3-wire control circuit figure illustrates a control circuit with multiple start and stop push buttons. In this circuit,
mu
ltiple normally closed stop buttons are placed in series and multiple open start buttons are placed in parallel to operate a
magnetic motor starter in VFD. This is a common application of a 3-wire control circuit in which you need to start and
stop the same VFD/motor from multiple locations within a facility. The 3-wire control circuit can be used in a variety of
ways to meet specific circuit application.

Allen-Bradley PowerFlex 755 Specifications

General

Category	AC Drive
Amperage	2.2…1470 A
Output Voltage	0 to Input Voltage
Output Current	2.2…1470 A
Enclosure	IP20, IP30, IP54
Communications	EtherNet/IP, ControlNet, DeviceNet
I/O	Digital, Analog, Encoder, Relay
Safety	Safe Speed Monitor
Protection Features	Overcurrent, Overvoltage, Undervoltage, Overload, Short Circuit, Ground Fault, Overtemperature
Operating Temperature	-10°C to 50°C (14°F to 122°F)
Storage Temperature	-40°C to 70°C (-40°F to 158°F)
Humidity	5…95% noncondensing
Altitude	Up to 1000m (3300ft) without derating
Voltage	200-240V AC, 380-480V AC, 500-600V AC, 690V AC
Input Voltage	200-240V AC, 380-480V AC, 500-600V AC, 690V AC
Control Method	Sensorless Vector