An OEM is redesigning its feeder conveyor line for the food industry. Marketing wants to sell these units to Asia, Europe, and South America as well as the domestic market. That means a 60 Hz motor for North America and a 50 Hz power supply everywhere else. Does the OEM build two separate feeder conveyor lines, or one that accommodates both markets? Three options are available:
Build for the Market
The first option, market-specific feeder conveyors, allows supply chain flexibility. One line of feeder conveyors meets normal 3-phase power requirements for North America, i.e. 460V, 60 Hz. Another line, based on a 400V, 50 Hz power supply, satisfies the export market.
A 1 hp (0.75 kW) 60 Hz 4-pole motor with 15:1 reducer, for example, supplies 116 rpm to the conveyor (1750 rpm ÷15). Because a 50 Hz motor with the same ratio reducer is slower (1425 rpm ÷15 = 95 rpm), the gearbox ratio must be changed to compensate. By designing and stocking motors, reducers, and electrical components for North American and export markets, separate feeder conveyor models can be built and supplied on demand. One advantage is that each machine can be manufactured to meet safety codes and approvals for the market where it is sold. Stocking parts for two different machines, on the other hand, makes a large inventory.
An alternative to this approach is the design and production of a custom motor, capable of operating from either 50 Hz or 60 Hz. A custom motor designed for both markets helps reduce inventory requirements but still requires separate gear reducers. Without changing reduction ratio, the conveyors will have different feed rates for 50 and 60 Hz operation. In addition, the machine's safety codes and approvals need to suit both markets where it is sold. Separate machine models for domestic and export sale would still be built.
One Conveyor Line, Two Markets
Powering the motor with an adjustable speed drive (ASD) such as the new Baldor H2 Inverter Drive provides the third approach. An ASD does not care if the power supply is 50 Hz or 60 Hz. Even when operated from 50 Hz input, the inverter can be programmed to deliver 60 Hz output to the motor, operating at the 1750 rpm. No gearing changes are needed. The addition of an ASD, therefore, allows the same motor and reducer to be used regardless of where the machine is shipped.
Furthermore, the H2 Inverter Drive can be used to adjust feed rates for different products, and will tie into process control schemes to automatically adjust rate as required by other equipment. Finally, adjustable speed drives offer a "soft start" feature that brings the motor to speed gradually. This, in turn, results in a gentle start for the conveyor to prevent items on the conveyor from tipping over. As with the custom motor option, the machine's safety codes and approvals need to be suited for the targeted market.
Applications such as the feeder conveyor point out the design choices available to the design engineer. Is there a correct "best" answer? The optimal solution depends on those features the designer wishes to build into the machine. The last configuration, using an adjustable speed drive, allows the most flexibility and creates a machine that could be used anywhere in the world.
Test your knowledge against Baldor's motor experts at http://rbi.ims.ca/4401-504