Vacuum motors in series

[Calypso]

Found this info on the web. May try it depending on the vacuum level I'm able to reach with normal setup. I have tangential discharge motors, so series would not compromise the motor cooling, because that can be handled separately by plumbing the exhaust in different chamber from where motors are and venting the motor box with ambient air.

60% increase in vacuum sounds tempting...

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Operation of Vacuum Motors in Air Series back to top

It is possible to connect two vacuum motors in air series by connecting they discharge of the first motor to the inlet of the second motor to increase the overall vacuum level in a cleaning machine. We have a number of customers that utilise motors in this manner in various types of equipment.
There are potential problems associated with the air series application of motors as it produces a severe thermal condition on the second motor. The discharge air from the first motor is quite warm and when it is ducted to the second motor, the heated air increases further in temperature due to the compression of the air in the vacuum system.

The high temperatures can have an adverse effect on the bearing system of the second motor. In addition, the high temperatures coupled with the increased pressure in the second motor can cause the grease to be forced out of the ball bearing at the bottom (fan end) of the second motor.

Depending on the effective operating orifice of the vacuum system, enough heat can be generated to cause deformation of the fan system that can lead to a fan strike or locked rotor condition.

Another problem is the electrical current required to operate the air series vacuum system. Special wiring assemblies and circuits may be necessary to carry the high current level when operating two motors in air series.

When two like motors are connected in air series, the sealed vacuum level will increase by approximately 60% from that of a single motor. Airflow at a wide open condition does not appreciably increase by operating two vacuum motors in air series.

Another problem frequently seen in air series applications is that adequate cooling air is not provided for the first or lower motor. Both motors must receive cooling air directly from outside the motor enclosure and there must not be any recirculation of motor cooling air. If the motors are not properly cooled, severe thermal problems can develop in the motors.

Applications using vacuum motors connected in air series should be thoroughly tested to ensure the integrity of your design. There are potential problems with this type of application as noted above and these must be fully understood. Air series installations might have an adverse effect on the life of the motors and the reliability of your equipment.

[larrycavan]

I'd be interested to see how it works out for you. Please keep the board posted with your results.

Larry C