Pellerin Milnor Corporation

Technical Knowledge Base

Why We Use Inverter

Why Milnor uses inverters on welded CBWs
1. IN-RUSH CURRENT: Without an inverter, the in-rush current of the welded CBW was up to seven times the full load amps of the connected motors. Since many customers pay their electric bill based on "peak demand," this caused a substantial increase in their electric utility costs.

The 50 kilo CBW uses "soft start" by starting half of the motors at one time and turning on the other half at "halfm" time. This substantially reduced the in-rush current provided by the 2 or 3 hp motors utilized on the 50 kilo machine.

2. OVER ROTATION: The welded CBW has less friction to overcome since it only has two L-seals, two chains and two gear reducers per module section. In the case of a 4 module machine, this reduces the total "friction" by two. Remember, L-seals were on both sides of each module which reduces that friction by four.

The result of this "lack of friction" was a severely over rotated machine when no goods were inside, up to 50 degrees in rotation angle in an unloaded and loaded CBW.

The possible results of over rotation are (1) foul transfers, (2) reduced washing action [because the rotational proximity switches were set close together to accommodate the huge over rotation] and (3) water transferring forward via the scoop when the machine was allowed to over rotate.

To accommodate the "empty machine over rotation", we did move proximity switches to reduce the rotational arc. The result was a washing angle of slightly over 190 degrees with a loaded machine.

The inverter allows us to decelerate the basket electronically (through the inverter) to stop the over rotation. Now the empty and full machine rotation angle should be very close to the same. However, the factory had continued to set a "shallow" rotation angle after inverters were applied until the last week of December 1994. This would indicate that there are many inverter driven CBW's which "under rotate". (See the proximity switch setting instructions under How do I?)

Last updated: 07/25/2005 / Node ID: 125 / Key Chain: