Research & Design

ATB LS machines are manufactured in accordance with IEC 60034. Where specified, however, machines can be supplied to meet NEMA, API and other national and international standards, as well as contractors’ and end users’ specifications.

Four Pole Synchronous Machines

Our synchronous machines can be supplied for nominal power 10MW to 30MW, voltages from 2.3 to 15kV, and 1800 rpm, complete with air or water-cooling systems. As standard, machines are designed for Class B rise using Class F insulation (IEC 60034-1).

Variable speed machines are a requirement for many compressor and pump packages, and ATB LS has vast experience of these applications. Electronic drives (inverters) allow conventional motors to be operated at variable speeds, VSD synchronous motor packages are available from ATB LS. The motor electrical design can be optimised to suit the specific inverter operation and driven requirement.

Low Starting Current

We have designed and manufactured some of the largest motors with reduced starting current. Applications of LS’s low starting current design have been installed on many offshore platforms or FPSO, where the power generation is limited or onshore facilities fed from low capacity lines. Use of DOL low starting current design can provide a cost-effective solution removing the need for expensive electronic variable frequency starters or other forms of soft starters.

In conjunction with the system designer and the driven equipment designer, motors with starting currents down to 240% of full load current have been produced which minimise the impact on the line during starting of the motors but with sufficient torque to accelerate the driven equipment up to full speed.

At the time of writing LS have approximately 240 motors with starting current ranging from 250% to 450%, which have been commissioned for operation around the world. The ratings range from 500kW to over 15MW. One of the lowest starting current designs was a 10.6MW motor driving a gas compressor for a FPSO. The starting current of this motor was 270% of full load current.

What is Needed to Start?

The table compares the requirement for the various options of starting method. A low starting current design removes the need for additional
starters, control gear and switchgear, thereby keeping capital and maintenance costs to a minimum.

Type of Start Switch Gear Control Gear
DOL - Low start current motor 1 contactor None
Star-Delta (LV) 2 contactors Timing only
Reactor 2 contactors Reactor & timing
Auto Transformer 3 or 4 contactors Auto-Transformer & timing
Soft starter 1 contactor Soft starter (variable voltage)
Variable Speed Starter 1 contactor Complex (Full variable voltage & frequency Drive)