Hitachi SJ700-2 instruction manual B052

Chapter 4 Explanation of Functions

<2> DC voltage constant control during nonstop operation at momentary power failure (b050 = 02: no restoration, b050 = 03: restoration to be done)

- If momentary power failure occurs or the main circuit DC voltage drops during inverter operation, the inverter decelerates the motor while maintaining the main circuit DC voltage at the level specified as the target nonstop operation voltage at momentary power failure (0V-LAD stop level) (b052).

- This function starts operating when all the following conditions are met: -- "02" or "03" has been specified for b050.

-- The inverter is running. (This function does not operate if the inverter has been tripped, is in undervoltage status or stopped.)

-- The control power fails momentarily or the main circuit DC voltage drops to the DC bus voltage trigger level during power loss (b051) or less.

- This function operates when the conditions above are met even if the J51 connector cables have been disconnected from terminals R0 and T0, and cables are connected from main circuit terminal P to terminal R0, and from main circuit terminal N to terminal T0.

- If momentary power failure only lasts a short time, the inverter can continue operation without stopping its output. Conversely, if momentary power failure causes undervoltage, the inverter stops its output immediately and ends the operation of this function. When power is subsequently restored, the inverter operates according to the selection of restart mode (b001).

- When "03" is specified for b050, the inverter can be restored to normal operation if the input power is recovered from momentary power failure before the inverter stops its output. The inverter, however, may decelerate and stop the motor if a specific setting has been made for b051. The table below lists the differences in operation according to the setting of b051.

b050	b051	Operation
02 (No	b052 > Main circuit DC voltage at input power recovery	Decelerating and stopping the motor (DC voltage
		constant control) (Example 1)
restoration)
	b052 < Main circuit DC voltage at input power recovery	Decelerating and stopping the motor (Example 2)
03 (Restoration	b052 > Main circuit DC voltage at input power recovery	Decelerating and stopping the motor (DC voltage
		constant control) (Example 1)
to be done)
	b052 < Main circuit DC voltage at input power recovery	Decelerating and stopping the motor (Example 2)

- When this function operates and the inverter decelerates and stops the motor, the motor is forcibly stopped even if the FW signal is on. To restart the motor, turn on the FW signal again after confirming the recovery of inverter input power.

Note 4: Each of the values of b051 and b052 must be the undervoltage 210V(200V class),410V(400V class)level or more. This function does not operate when undervoltage occurs. The value of b051 must be less than that of b052. When b051 is much higher proportional gain (b055) results in overcurrent by rapid acceleration after this function operates.

Note 5: When "02" or "03" is specified for b050, PI control is performed so that the internal DC voltage is maintained at a constant level.

-Setting a higher proportional gain (b055) results in a faster response. However, an excessively high proportional gain causes the control to diverge and results in the inverter easily tripping.

-Setting a shorter integral time (b056) results in a faster response. However, an excessively short integral time results in the inverter easily tripping.

-Setting a lower proportional gain (b055) results in undervoltage trip due to a voltage drop immediately after starting this function.

(Example 1)

Voltage across main circuit terminals P and N

Vpn(V)

DC voltage across main circuit

Recovery of input power

Period of DC voltage

constant control

Output frequency

(Hz)

b050=02,03 (decelerate to stop)

Recovery of input power

(Example 2)

Voltage across main circuit terminals P and N

Vpn(V)	DC voltage across main circuit
b052	Recovery of input power
b051
		Period of DC voltage
Time		constant control
Output frequency
(Hz)
		b050=03(running)
		b050=02
Time		(decelerate to stop)
		Recovery of input power

b052

b051

Time

Time

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