Acceptable Voltage dip
Acceptable Voltage dip
(OP)
When doing calculations for voltage drop when motor starting, I have always used figures of 20% at motor terminals or 15% at the switchboards as maximum allowable.
Can anyone tell me if there is a British Standard that actually defines the allowable voltage drop and time periods when motor starting?
Many thanks
Matt
Can anyone tell me if there is a British Standard that actually defines the allowable voltage drop and time periods when motor starting?
Many thanks
Matt






RE: Acceptable Voltage dip
There are limits within which the machine should be capable of delivering its rated power output and rated starting torque, but that is a slightly different question. I think there's a voltage-frequency chart in 60034-1 and the machine should be capable of meeting its design spec over +/-5% voltage and in the range 49 - 51Hz although possibly not both extremes simultaneously: 95% voltage at 51Hz would result in moderate underfluxing and high slip, and 105% voltage at 49Hz would result in stator iron saturation and overheating.
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If we learn from our mistakes I'm getting a great education!
RE: Acceptable Voltage dip
I was thinking more of the dip on the switchboards affecting other equipment when using a weak supply such as a generator. Contactor mfrs often quote figures of acceptable control voltage before they drop out.
Voltage dips can cause re-strikes on sodium lighting etc.
I was wondering if these limits were defined anywhere or just different mfrs recommendations?
RE: Acceptable Voltage dip
The Energy Networks Association publishes documents on behalf of the distribution companies: Engineering Reccomendation P28 details the planning limits for disturbances to the public system caused by consumers, P29 deals with planning limits for voltage imbalance caused by consumers, G5/4 deals with planning limits for voltage harmonic distortion caused by consumers equipment.
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If we learn from our mistakes I'm getting a great education!