Start with motor current, then check duty

Build a requirement from the motor nameplate

Start with the motor voltage, connection, rated current, frequency and speed. Record the load and the required speed range separately. A kilowatt label alone cannot resolve differences in motor efficiency, duty or supply. Photograph the nameplate and retain its units rather than converting uncertain values into a confident specification.

Separate continuous duty from short overloads

Continuous current answers whether the drive can sustain normal operation. An overload percentage answers a different question and only has meaning with its reference current, duration and operating conditions. Ask for acceleration time, repeated start frequency and the interval available for cooling. A conveyor that starts loaded and a centrifugal fan need different application discussions even when their motors carry the same power rating.

Work through an illustrative current calculation

Suppose a hypothetical motor needs 12 A continuously and the process briefly needs 18 A for 30 seconds. A candidate rated at 13 A with a documented 150% overload for 60 seconds would have a nominal overload figure of 19.5 A. Those numbers justify further review; they do not establish suitability. Check the permitted repetition rate, initial temperature, output frequency and any current reduction from the installation. This is a worked example, not a rating for a listed product.

If installation derating reduces the same hypothetical continuous rating by 10%, the available value becomes 11.7 A. It is then below the stated 12 A requirement. Do not apply this illustrative percentage to a real model: obtain the manufacturer's derating method and conditions. Where multiple factors apply, ask how they combine rather than multiplying assumed percentages.

Read the correct column in the manual

The SINEE EM730 V100 manual separates heavy-duty and light-duty output-current values in its model table. Preserve that distinction when comparing a quotation. Record the model suffix and the table revision with each value; do not take one model's current and another model's power to construct an apparently compatible drive. A series range is useful for discovery but cannot replace a model row.

Resolve installation limits before ordering

Ask about enclosure ventilation, ambient temperature at the drive, altitude, cable length, output filtering and braking requirements. Keep full-output temperature separate from the maximum permitted temperature with derating. If the cabinet is enclosed, room temperature may not describe the air actually entering the drive. Request dimensions and heat-loss information for the selected frame size.

Send a complete sizing request

Include the motor nameplate, supply conditions, normal load, acceleration/deceleration times, overload event and repetition interval. State the cabinet environment and required network. Ask the supplier to return an exact model code, applicable current and overload table, all required options and a written explanation of unresolved conditions. Compare the returned scope before comparing price.

Use the directory's unknown state

A missing overload duration or ambient limit remains a question. Narrow the directory using documented values, then include unconfirmed entries only when you are prepared to resolve their gaps. A matching filter result is a match to the recorded fields, not approval of the complete electrical installation.