Cubs roar into three-phase arena

IMO has unveiled a new generation of its compact Jaguar Cub drives - 18 years after the first Cub made its debut. The latest generation extends the family into three-phase applications, adds technical enhancements including a new control system, and undercuts the prices of previous models.

The new Cubs span single-phase ratings from 0.37-2.2kW and three-phase ratings from 0.37-4kW. Integral EMC filters are available for all models, and integral braking resistors for models above 1.5kW.

The drives use a new control philosophy called Simplified Torque Vector (STV), which uses an advanced magnetic flux estimator, and slip compensation with auto-boost, to deliver starting torques of 150% or more. STV is said to result in low torque ripple, improved dynamic operation under varying loads, and reduced motor stress and losses.

Considerable effort has gone into extending the life of the new drives and providing preventative maintenance information to avoid unscheduled downtime. For example, the fans use a new bearing design that prevents the ingress of dust, and are designed to operate for at least 60,000 hours - equivalent to about seven years of operation. The drives have a five-year warranty.

A variety of maintenance information is provided via the drives` four-digit LED display, including hours run, heatsink temperatures, the number of starts, maximum currents and data on the fan and capacitors.

A current limiter that is independent of torque or frequency helps to prevent mechanical damage. The drives are also protected against phase losses, short and open circuits, and earth faults.

Other features include: soft switching; 24V DC power terminals; 400Hz operation; three-wire control; an analogue output for applications such as PID feedback; a programmable changeover relay; RS-485 and Modbus RTU communications; and fifth-generation IGBTs with reduced heat losses.

The new drives, which are being built for IMO by Fuji Electric, are less expensive than their predecessors. For example, a typical sub-1kW single-phase model is about 20% cheaper, while three-phase savings are even greater because IMO did not offer three-phase Cubs before. In some cases, the savings compared to its previous lowest-cost three-phase models are as much as 45%.

The new Cubs will be followed by other new Jaguar drives ranges later this year and in early 2005, including models aimed at lift and HVAC applications.