The electrical isolation of the MM4 products meets or exceeds the safety requirements of EN50178 and related standards.
On all MM420 and MM411 units the isolation between control and power circuitry is achieved using optical isolators, therefore the leakage current is not normally measurable.
This is also the case for MM440 units, frame size F.
However, MM440 frame sizes A, B and C use resistors to monitor the DC link giving an impedance of approximately 3.4 M Ohms on 400V units and 1.6 M Ohms on 230V units.
Similar measurements may be observed on Frame Sizes D and E.
Identical measurements are observed on MM436 (SED2) and MM430 drives of corresponding frame sizes.
Px Drives (MM440 Fx and Gx 90 -200kW) have an impedance of approximately 3.7 M Ohms between control and power.
Please bear in mind that if several drives are connected to a system, an impedance less than 1M Ohms may result.
This impedance, which may be measured during certain acceptance tests, may be considered too low for, for example, marine applications.
These currents are not related to the high frequency currents that flow to earth during normal operation of the drive.
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