BMU series for conveyor application

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BMU series for conveyor application

Postby om_tech_support_JT » Thu Aug 07, 2014 6:07 pm

Q: Hello, currently I run at 2 speeds with my motor on a vertical conveyor for sorting parts, and on one of them I have the need to manually slow the motor down and then speed it back up. This has been done with a stepper motor controlled through a PC via keyboard commands. I've been reading the manual on this BMU460SA-50A-3 system and it looks like a very promising replacement for my current control system. If I understand correctly you can have 4 preset rotation speeds / directions and can also vary the speed both up and down on the fly, correct?

Your info states a rated torque of 76 lb-in and a Permissible Load Inertia of 12000 oz-in². If I understand Permissible Load Inertia right, this would be how much of a work load is in the system that the motor is able to overcome to start rotation, correct? I've attempted to look up "oz-in²" to understand better if this value is greater than, or less than the motors rated torque of 76 lb-in. I've not had any luck. Would you be kind enough to clarify?

Also can the driver accept inputs from limit switches?

A: Thank you for your interest in our new BMU series! Yes, the BMU series system is capable of varying speeds on the fly by operating the front panel on the driver, or it can run up to 4 preset speeds in external input mode. For vertical loads, it can also generate some holding torque at the motor when stopped. However, since this is an electrical brake; not a mechanical brake like our electromagnetic brakes. If the power fails, and you're lifting a heavy load with the motor, the load may drop thus causing safety issues. Our manual recommends against using the BMU series to move a load vertically for this reason. The gearhead will provide some holding torque due to friction but most likely not sufficient to hold your load. For vertical loads, we would suggest something more reliable like the BX, BLE, or BLV series brushless motor and controller systems which includes electromagnetic brakes.

Here's an OVERVIEW page for all our brushless motor systems: ... index.html

Your understanding of inertia is correct. Inertia is a resistance to a change in speed. The motor has to overcome the inertia in order to start rotation, but the same effect also occurs during stopping.

76 lb-in is a torque unit. This means the motor can rotate a 76 lb load if the load is 1" away from the rotational axis. 12,000 oz-in² is an inertia unit. These are treated differently in our literature. As long as your required torque stays under 76 lb-in, and your inertial load is under 12,000 oz-in², the motor will work. Our brushless motors have built-in hall-effect sensor feedback, so if you exceed the permissible load inertia for the motor, the driver will most likely generate alarms and prevent operation. Inertia is also used to calculate acceleration torque. Total required torque = load torque (constant torque) + accel/decel torque.

Here are some motor sizing forms on our website to help you calculate your inertia, torque, and speed requirements. Once you have these requirements, we can then confirm your motor selection. If you're interested in more details regarding calculation of motor requirements such as torque and inertia, I have inclued a 2nd link for formulas and examples.

-registration is required.


The BMU series does not offer any home or limit sensor inputs. For limit switches to work, you'll have to go through a relay and have it turn either the FWD or REV input off when a limit is triggered.

If you have any questions, please do not hesitate to contact our knowledgeable technical support group.

PHONE: 800-468-3982

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