Oriental Motors introduces vector control for small dc brushless motors

The new controllers are called BLH2D (in photo right).

“Adopting vector control as the motor control method enables BLH2D to control the current phase,” said Oriental Motor. “This allows processing of regenerative power and torque limiting” and “BLH2D can reduce a vibration of audible frequency of 20 Hz to 20 kHz compared with the conventional model.”

While the earlier BLH could not brake, control with BLH2D is four-quadrant: active acceleration and active braking in both rotational directions.

When actively braking, the motor acts as a generator, and the controller can handle this regenerated power in three pre-settable ways:

The first prevent it from being fed back into the up-stream power supply by setting the current vector to turn the energy into heat inside the motor. In this situation, a mosfet in the front-end (left) ensures power cannot be forced back.

If the motor cannot handle the extra heat, a coasting stop is available. Braking is weak, and similar to  deceleration using the earlier model.

If the motor cannot handle the extra heat and strong breaking is required, or energy needs to be returned to an up-stream battery, full regenerative braking is also available.

Unlike the older type, in-rush current limiting is provided (also diagram above left), reducing inrush by as much as 95%.

Three interface options are available, depending on model:

A back-compatible analogue control version, allowing speed control from a potentiometer or an external voltage. “The power supply cable, the IO cable and the motor cable are compatible with the conventional [BLH] model. The deceleration movement is coasting to a stop as with the conventional model,” said Oriental.

There is a digital type for which the company has published little information. It can be controlled at least via PWM, and “analogue speed adjustment is still possible”, said the company. It can be set up via USB using the company’s ‘MEXE02’ software running on PC. “Calculated load factor can be displayed and checked using the status monitor function of the MEXE02 software. If irregularities are detected, predictive maintenance can be initiated.”

A further digital version adds an RS-485 interface to what ever the digital version can do. This can work with similar, but not identical, cabling to the analogue type, and “is primarily intended for applications where the status of the drive is to be constantly monitored or the commissioning effort is to be kept low. It can be used to upgrade systems and replace an existing BLH model”, Oriental said.

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