Danfoss VLT AutomationDrive FC 301 Design Manual

Also see for VLT AutomationDrive FC 301: Programming guide Installation guide Operating guide Installation guide Design guide

Contents

Danfoss VLT AutomationDrive FC 301 Design Manual Manual pdf 57 page image

All control terminals and relay terminals 01-03/04-06comply with PELV (Protective Extra Low Voltage), with theexception of grounded Delta leg above 400 V.Galvanic (ensured) isolation is obtained by fulfillingrequirements for higher isolation and by providing therelevant creepage/clearance distances. These requirementsare described in the EN 61800-5-1 standard.The components that make up the electrical isolation, asdescribed below, also comply with the requirements forhigher isolation and the relevant test as described in EN61800-5-1.The PELV galvanic isolation can be shown in 6 locations(see Illustration 5.7):To maintain PELV, all connections made to the controlterminals must be PELV, e.g. thermistor must bereinforced/double insulated.1. Power supply (SMPS) incl. signal isolation of DC-link.2. Gate drive that runs the IGBTs (triggertransformers/opto-couplers).3. Current transducers.4. Opto-coupler, brake module.5. Internal inrush, RFI, and temperaturemeasurement circuits.6. Custom relays.7. Mechanical brake.130BC968.101325 46baM7Illustration 5.7 Galvanic IsolationThe functional galvanic isolation (a and b on drawing) isfor the 24 V back-up option and for the RS-485 standardbus interface.WARNINGInstallation at high altitude:At altitudes above 2,000 m, contact Danfoss regardingPELV.WARNINGTouching the electrical parts could be fatal - even afterthe equipment has been disconnected from mains.Also make sure that other voltage inputs have beendisconnected, such as load sharing (linkage of DCintermediate circuit), as well as the motor connection forkinetic back-up.Before touching any electrical parts, wait at least theamount of time indicated in Table 2.1.Shorter time is allowed only if indicated on thenameplate for the specific unit.5.5 Brake FunctionsBraking function is applied for braking the load on themotor shaft, either as dynamic braking or mechanicalbraking.5.5.1 Selection of Brake ResistorThe brake resistor ensures that the energy is absorbed inthe brake resistor and not in the frequency converter. Formore information see the Brake Resistor Design Guide.If the amount of kinetic energy transferred to the resistorin each braking period is not known, the average powercan be calculated on the basis of the cycle time andbraking time also called intermittent duty cycle. Theresistor intermittent duty cycle is an indication of the dutycycle at which the resistor is active. Illustration 5.8 shows atypical braking cycle.NOTICEMotor suppliers often use S5 when stating thepermissible load which is an expression of intermittentduty cycle.The intermittent duty cycle for the resistor is calculated asfollows:Duty cycle = tb/TT = cycle time in stb is the braking time in s (of the cycle time)System Integration VLT® AutomationDrive FC 301/FC 302 Design Guide, 0.25-75 kWMG33BF02 - Rev. 2013-12-20 555 5