diff --git a/pandapower/control/controller/trafo/ContinuousTapControl.py b/pandapower/control/controller/trafo/ContinuousTapControl.py
index b1bb7c5d5..7c77e2714 100644
--- a/pandapower/control/controller/trafo/ContinuousTapControl.py
+++ b/pandapower/control/controller/trafo/ContinuousTapControl.py
@@ -4,6 +4,7 @@
 # and Energy System Technology (IEE), Kassel. All rights reserved.
 
 import numpy as np
+
 from pandapower.auxiliary import read_from_net, write_to_net
 from pandapower.control.controller.trafo_control import TrafoController
 
@@ -97,6 +98,8 @@ def is_converged(self, net):
             return True
 
         vm_pu = read_from_net(net, "res_bus", self.controlled_bus, "vm_pu", self._read_write_flag)
+        # this is possible in case the trafo is set out of service by the connectivity check
+        is_nan =  np.isnan(vm_pu)
         self.tap_pos = read_from_net(net, self.trafotable, self.controlled_tid, "tap_pos", self._read_write_flag)
         difference = 1 - self.vm_set_pu / vm_pu
 
@@ -110,4 +113,4 @@ def is_converged(self, net):
         else:
             converged = np.abs(difference) < self.tol
 
-        return np.all(converged)
+        return np.all(np.logical_or(converged, is_nan))
diff --git a/pandapower/control/controller/trafo/DiscreteTapControl.py b/pandapower/control/controller/trafo/DiscreteTapControl.py
index 48ef2bb07..cf4aa2353 100644
--- a/pandapower/control/controller/trafo/DiscreteTapControl.py
+++ b/pandapower/control/controller/trafo/DiscreteTapControl.py
@@ -3,9 +3,11 @@
 # Copyright (c) 2016-2023 by University of Kassel and Fraunhofer Institute for Energy Economics
 # and Energy System Technology (IEE), Kassel. All rights reserved.
 import numpy as np
+
 from pandapower.auxiliary import read_from_net, write_to_net
 from pandapower.control.controller.trafo_control import TrafoController
 
+
 class DiscreteTapControl(TrafoController):
     """
     Trafo Controller with local tap changer voltage control.
@@ -115,6 +117,8 @@ def is_converged(self, net):
             return True
 
         vm_pu = read_from_net(net, "res_bus", self.controlled_bus, "vm_pu", self._read_write_flag)
+        # this is possible in case the trafo is set out of service by the connectivity check
+        is_nan = np.isnan(vm_pu)
         self.tap_pos = read_from_net(net, self.trafotable, self.controlled_tid, "tap_pos", self._read_write_flag)
 
         reached_limit = np.where(self.tap_side_coeff * self.tap_sign == 1,
@@ -125,5 +129,4 @@ def is_converged(self, net):
 
         converged = np.logical_or(reached_limit, np.logical_and(self.vm_lower_pu < vm_pu, vm_pu < self.vm_upper_pu))
 
-        return np.all(converged)
-
+        return np.all(np.logical_or(converged, is_nan))