Beckwith M-0067E On Load Voltage Regulating Controller Selection and Debugging Guide

The compensation setting needs to be calculated based on the impedance of the feeder and the CT ratio, usually determined through on-site testing or short-circuit calculation. The factory defaults to an accuracy of ± 5% for amplitude and ± 2% for phase angle.

Parallel operation and circulation control

When two or more transformers are running in parallel, it is necessary to avoid excessive circulating current caused by inconsistent tap positions. M-0067E provides a dedicated 'Circulating Current Input', which uses another 0.2A CT input with a burden of only 0.005VA. This input detects the circulating current between transformers and generates a correction signal of approximately 24V (corresponding to 0.2A) with a phase lag of about 90 °, used to coordinate various transformer taps and minimize the circulating current.

When running in parallel, each controller needs to share the circulating current signal through a common CT or interconnect circuit. The specific wiring method should refer to the manufacturer's application notes.

Voltage Reduction Function

M-0067E supports automatic reduction of output voltage by 1-3 steps under specific conditions (such as system light load or energy-saving requirements). Optional configurations include:

One or two-step voltage reduction: preset internal resistance.

Three step voltage reduction: An external resistor (provided by the factory) needs to be added.

Instantaneous voltage reduction (without delay): Factory installed dedicated circuit.

This function can be activated through external contacts or timed programs, and is suitable for reducing the voltage of the distribution network at night or during non peak hours to save energy consumption.

Testing and diagnostic functions

The "TEST/OPERATE" switch on the panel can be switched to the testing position. At this point, the line voltage drop compensation is disabled and a non calibrated voltage adjustment knob is provided to manually change the internal reference voltage. Users can connect a high internal resistance voltmeter (≥ 500 Ω/V) to the test terminal and observe the lighting boundaries of the "up" and "down" LED indicators to verify whether the bandwidth setting is accurate. This method does not require external testing sources, greatly facilitating on-site verification.

Common on-site problems and solutions

7.1 Controller does not operate, LED indicator light does not light up

Possible reasons and investigation:

Power supply missing or low: Check if the PT secondary power supply is normal (>60Vac, output is locked below this value).

Voltage within bandwidth: Measure whether the difference between the actual voltage and the set center value is less than half of the bandwidth.

Timer not started: If the voltage exceeds the limit but the timer does not start, check the mode settings and cam switch logic.

Damaged output relay or disconnected external circuit: Check the output terminal voltage and motor starter coil.

7.2 Frequent movements or oscillations

Usually caused by the following factors:

Narrow bandwidth setting: Increase the bandwidth appropriately.

Improper setting of line voltage drop compensation: If the compensation amount is too large or the phase angle is incorrect, it may lead to overshoot. R/X compensation value needs to be recalculated.

Timer too short: Increase delay time to avoid short-term fluctuations.

CT polarity or wiring error: causing compensation direction error, check the CT secondary wiring and the position of the Directive/REVERSE switch.

7.3 Large voltage control deviation

Check the accuracy and wiring of PT: Ensure that the PT secondary voltage accurately reflects the bus voltage.

Center value calibration: Compare with a standard voltmeter and adjust the panel potentiometer if necessary.

Compensation settings do not match the actual circuit: recalculate impedance and adjust potentiometer.

Key points for installation and operation

8.1 Mechanical Installation

M-0067E is designed for standard vertical or horizontal installation, with panel opening dimensions of 5-7/8 "x 15-1/8" (width x height) and external dimensions of 6-3/8 "x 16-1/2" x 3-1/16 ". During installation, ensure good ventilation and avoid direct sunlight and strong heat sources.

8.2 Electrical wiring

Power supply: taken from the PT secondary side (90~140Vac), note that polarity can be ignored, but ensure correct phase (recommended to be in the same source as the voltage input).

Voltage input: directly connected to PT secondary (usually 120V).

Current input: CT secondary requires a rated value of 0.2A. If the on-site CT is 5A or 8.66A, an auxiliary CT (M-0121 or M-0169) needs to be used for conversion.

Circulation input: When used in parallel, 0.2A CT is also required.

Output contacts: Control the boost and buck contactors separately, with a contact capacity that can drive NEMA Class 1 starters or smaller.

8.3 Pre operation inspection

Confirm that the power supply voltage and frequency (50/60Hz optional, default 60Hz) are correct.

Check the CT ratio and auxiliary CT wiring to ensure that the current direction is correct (K-L polarity).